A further great way to explain it is in terms of the 2010 midterm elections.

Obama was completely unable to pass healthcare, because he had a similar dynamic that Trump has right now.

The Republicans weren't playing ball, and there were a few Democrats rustling feathers too.

However, in 2010, Democrats won big! And were able to keep a super majority for a few months (because of contested elections, then... I think it was Lautenberg died and Christie appointed a republican) and they were able to pass their healthcare bill (the ACA, Obamacare).

So, if the Republicans are able to win every state Trump won in the presidential of those seats (in the senate) they will have enough to have a super majority (that they don't have right now) and will be able to pass their legislation.

If they don't, they will have to work with the democrats (who don't seem interested in working with the GOP at all). to pass something to show for it. Otherwise, Trump will be a two term lame duck. (Maybe even one term if things go that bad)