Being a UK citizen, I am not totally familiar with the American political system, but what would happen if Trump lost in the midterms?

Trumps term is 4 years.
The midterms are for reps and senators.
Dems could win more seats in house and majority in the senate (51).
Trump would have a difficult time putting legislation through.
Dems would also waste more time and money attempting to impeach trump

The same two parties will always run the USA because the voters refuse to vote outside that box. The Dems are exactly like Trump on wars.