Few things here.

1. The war didn't take Congressional action to start. Bush started it unilaterally and was later authorized in a bipartisan manner.
2. Republicans almost always act as a unified block regardless of what's happening. There was one or two that acted like they might not vote with them but still had a 95%+ voting record. That's why it was so amazing when John McCain prevented the killing of the ACA.
   3.The Senate heavily favors Republicans because of the number of small states so it's much easier for them to get 50+ members and the house mildly favors the Republicans because of gerrymandering.
3. It's easier to kill things and change the tax code than pass positive programs/laws. Because funding/tax bills have to originate from the House, the Senate historically just requires an up/down vote instead of requiring 60 votes like normal. This in association with 2 means programs can be starved of funding and tax changes are much easier for Republicans.
4. Democrats will vote for Republican sponsored things if it benefits the people. Like keeping the government open or the minor crime reform bill the was passed during Trump. The reverse largely isn't true.

This isn't defeatist. It's a realistic understanding of how the systems work. The fact that we got so many major things passed with such a tiny amount of control and in such a small amount of time is amazing.