My understanding is that when the White House changes Party, the new Party always loses seats in Congress and maybe State Houses. Is this true?
Anyway, discuss the next national ordeal here.
Yes, this is true, and not just when the White House changes party. The party that wins the Presidency almost always loses seats in the midterm elections. Over the past 5 midterm elections in which a Democrat sat in the White House, the Democrats lost an average of 28 seats in the House and 5 in the Senate. For Republicans, it was 15 seats in the House, and 2 in the Senate. The Senate is much more variable, as it depends on which Senators are up for re-election that year. There are a few exceptions. In both 1998 (Clinton) and 2002 (Bush), the party in power gained seats in both houses. That is not the norm, as the only other year that the party in power won seats in the House during a midterm election was 1934!
Most recently, during the first midterm in the Obama presidency, the Democrats lost 63 House seats and 6 Senate seats. In 2018, the Republicans lost 41 House seats, but gained 2 Senate seats (only 9 of the 35 seats up for election were Republican held, and many of the Democratic seats were in states that Trump carried). Therefore, expect the Republicans to gain seats in both chambers in 2022.