I am wondering why the US or other countries have not done anything to keep Putin in check....any thoughts?

We haven't been obligated by an treaty to act in the Ukraine against Putin. I think once we shows any inkling of reaching beyond the Ukraine, we won't have much choice. Also, I think it's telling by how much military power we've moved into the area recently that we are definitely fronting that we will do something there if need be. Personally, I think the Ukraine is getting shafted, and we have more business there than many other places we've been going to recently.

With everything else going on around the world, is Putin that much of a "danger" anymore? Sure, we need to keep an eye on him but I'm sure people there are saying the same about us.

The US as part of NATO has been very active with many readiness exercises in the Baltic States and around the rest of Europe. These exercises are meant to show solidarity across the NATO Alliance and also serve as a deterrent to further aggression by Russia.