I don't find there is much support for the hypothesis that America pursued an empire from its inception. Quite the opposite, I believe I said that it went through a long period of isolationism, interrupted twice by the two world wars. I'm not aware of any political scientists or historians that dispute this conclusion or what evidence they present to the contrary. America did end up replacing the British empire, but that was long after that empire fell apart and other candidates for the position failed.
U.S. expansion in the 1800 must be taken in the context of colonial politics at the time and the fact that all nations at the time were doing the same thing: bringing more territory under a centralized government's control. That's what France, Germany, Hungary, Italy, Spain etc were doing at the time. The U.S. had an additional incentive to bring these territories under control because it was trying to keep other colonial powers out of its business. The Monroe doctrine was the only foreign affairs doctrine that United States had until WWII; that is this was a country that did not have guiding principals concerning relations with other nations outside of its immediate neighborhood for most of the 19th century. Hardly an empire in the making.
On the contrary there are lots and lots of people who would dispute everything you said above.
To start from colonial times. The core founders of our country were all members of the financial and aristocratic (for want of a better word) elite of the US colonies. As such there were steeped in the politics and educational norms of such elites from the continent. All of the major countries of the time were engaged in a often violent competition to determine which country would gain the upper hand in the attempt to build and maintain empire. The US colonies were a key part of the British empire and all of our founders were fully aware of it and in their attempt to gain independence they played the other major powers off against Britain. And the French especially used the Americans against the British for their own ends.
So, in the light of this scene, it is not surprising to find that Thomas Jefferson, in the 1790s, awaited the fall of the Spanish empire until “our population can be sufficiently advanced to gain it from them piece by piece.” From the very beginnings of our country the elites had in their minds that the way toi survive and prosper in this world required one to emulate as much as possible the geo-political strategies of the great powers. One looked for opportunity and then they acted. This is the story of the growth of our empire. First you establish yourself's as an independent entity and then you slowly climb the stairs towards the top. While one is on that staircase they are not yet an empire but that is certainly the goal. We just happened to succeed.
Now it is certainly true to state that the general American public and no interest or knowledge of empire building in the earlyu decades of the country's existence, but their opinion was not valued or sought by the Founders who regarded the common man with great suspicion and held their views on politics with distain. The elites of the US were always interested in more wealth and power and their goals were to eventually obtain it.
The Monroe Doctrine, which you dismiss for some reason, was one of the most blatant acts of imperialism in history. And it occurred in 1823 just after the Founders passed from the political scene. It's purpose was to lay the groundwork for US dominance of the Western Hemisphere. It was the beginning of the deliberate demolition of the Spanish Empire. At that time the Spanish and Portugese were slowly losing control of their Latin American colonies and it was an ideal time for the US to start to exert itself. By this time it was convienent for the British to assist the US as this effort by the US was in line with their competition with the Spanish in other parts of the world. The Monroe Doctrine specifically stated that further efforts by European nations to colonize land or interfere with states in North or South America would be viewed as acts of aggression, requiring U.S. intervention. So we are threatening war over control of about 20 independent countries. This can only be described as an act of imperialism. While the verbiage of the Doctrine was intended to appear as if we were protecting the Latin American countries from the Europeans the actual intent was to reserve the Western Hemisphere to US exploitation. As history has shown it was not done for the benefit of those countries but for the financial benefit of the US. Empire building.
When the US was negotiating the Louisiana Purchase in 1803 it insisted on the inclusion of Texas. Texas at the time, of course, was not French territory but Spanish. The boundary between Spain and the US was set at the Sabine River in 1819. But the US never intended to honor this agreement and US settlers were encouraged to cross the border and start settling in Texas. There were several attempts to raise armies to invade the territory of Texas at this time which never came to fruition. Following the Mexican war of independence from Spain Texas became part of Mexico. But US intentions never changed and US immigration grew constantly and it was not long before secession from Mexico was in the cards and the inclusion of Texas into the Union was on the table. As we know this succeeded and Texas became another conquest of the budding American empire.
It is also worth noting that the Louisiana Purchase qualifies as an act of imperialism as we did not expand into unoccupied territory.
The first instance of popularizing US imperialism was by President Polk and the build up to the Mexican-American war in 1846. There having been no proper justification for this war it was clearly an act of imperialism and resulted in the eventual annexation of California and other western territories via the Treaty of Guadalupe Hidalgo and the Gadsden purchase. If we ignore the extermination of the native -Americans this and Texas were the first instances of the US taking territory by force. From this point on in American history the public was at least partially aware of our ambitions to grow into a powerful nation. At the expense of anyone who got in our way. The public justifications for such actions are always couched in diplomatic terms to make them seem less harsh and predatory. But reality is what you do not what you say.
The overthrow of the Hawaiian monarchy was an over act of imperialism done at the behest of American Business interests. Empire building as well.
By far the most openly imperialist American President was Teddy Roosevelt, who long before he became president was openly imperialistic and advocated building a empire. He openly stated that if a country had the ability to control and manage large swaths of the world and chose not to do so was an act of cowardice.
Roosevelt's speeches fundamentally transformed popular opinion in the U.S. He equated imperialism with masculinity and ambition while denouncing isolationism as lazy and cowardly. Roosevelt argued that imperialists were not greedy but courageous instead. He claimed that "we do not admire the man of timid peace. We admire the man who embodies victorious effort." Roosevelt was trying to speak for the American people when he said those words. And owing to his reputation as a war hero and his immense popularity, he succeeded. Americans embraced first his words and then later his policies.
Roosevelt was one of the main instigators of the Spanish-American war of 1898 which was an open act of aggression and was to fulfill the desires of Thomas Jefferson to strip the Spanish of their colonies. The end result was US control of Cuba, Puerto Rico and the Philippines. Empire building became mainstream. "Speak softly and carry a big stick." was not the mantra of a President who was a benign player on the world stage. They were the words of a man who believed taking advantage of the weak for gain was the manly thing to do.
Over the next 70 years the US acted much the part of the colonial empire builder. It actively worked to control and/or overthrow dozens of governments in Latin America (some many times over) in order to ensure that the countries were operated in a fashion which ensure profits for US business and access to raw materials. US maries and soldiers were used on dozens of occasions from across the world during this time for control of various colonial enterprises. The US took control of the territory of what is now Panama away from Columbia in order to create the state of Panama and have firm control of the location of the future Panama Canal (reminds you of the British and the Suez canal).
The end results of WWI and WWII clearly resulted in vast growth in America's wealth and influence around the world. The end result of these wars brought additional countries under the sway of US influence and control. Mostly to the benefit of US financial and business interests. This was not a bug but a feature. US dominance of the global financial structure following WWII and the creation of the IMF and World Bank (modern versions of the financial control exerted by the British at the height of their empire) which are controlled by the US and who's methods of financial assistance to the underdeveloped world (those weak countries Teddy thought we should take advantage of) works to keep them in a much lower state of development than is actually possible results in a shifting of their wealth and resources to the industrialized world at low cost. This is modern colonialism and a further demonstration of the US empire.
I hardly should need to say that the incredibly bloated US military, which is many times the size needed to provide sovereign security, is primarily for the purpose of maintaining and furthering our empire. American freedom and security have not been meaningfully threatened since WWII and even then the outcome was not in doubt. Our overseas garrisons and naval structure are very similar to those of Britain at the height of their power. We are pouring excess amounts of resources into military power as our hold on our empire is stressing and starting to crumble. A standard mistake that empires usually make at this stage of existence.
While our empire does not use identical structures or organizations or names for all that it does which match those used by the British it still has all the same functions. While the elites of the country are once again pursuing their goals of power and wealth, and the public has once again fallen asleep to reality and are ignored and their opinions not sought or valued, we are still on our path of power envisioned by Thomas Jefferson.
It just is what it is and I see no reason to deny it or ignore it.
What I am interested in, and why I started this topic, are the signs of coming impacts on the empire and how it affects events going forward. Everyone in the world will be impacted by what happens to us and how we deal with it. A very uncomfortable position to be in for others and potentially for us as well.