Congress is likely to flip for many reasons. This is just a drop in the bucket. Places like Wyoming aren't on the table. Republicans are in a jam because nobody can challenge Trump without being primaried.

The real problem for Trump and Republicans is they do great when Trump himself is actually on the ticket. That's his power. Unfortunately for him, he will never be on a ticket ever again. But he still holds considerable influence over primary voters. Primary voters don't win marginal States. Trump is a paper tiger but because of his control over primaries Republicans are trapped.