The US isn't reliable for at least 2 decades, pulling out of all kinds of treaties unilaterally, and it is known every 4 years a vastly different administration may come in. No state can make deals with such a fickle entity. And that will reliably isolate the US for a long time to come.

But let me back-peddle slightly (as nobody is arguing my point yet, and I want to refine it).

If the US gave Ukraine secret warning that they will pull out on a certain date, and to settle with Russia before that date, and Ukraine decided to keep fighting anyways, then I put no blame on the US. It has to be possible for the US to choose to not be involved, and giving plenty of heads up is the right thing to do. That heads up has to be covert so that Russia can't anticipate anything. So that means we would not have heard about it. As an average citizen without access to top secrets, I can't say if that happened or not, so I can't absolutely claim Trump is bad here. Just that it looks bad.