As for Russia not being as big a concern as Iran...talk about exactly what Putin wants the RW nutters to think.
Putin's a Christian, he doesn't like homosexuals, he believes in slapping a ho, and probably supports the right to keep and bear arms!
We are bound by treaty to protect Poland and Romania as well as Japan and S. Korea. The gray space with Ukraine and Taiwan is that I have heard several times in recent days: "America would never shed blood over X or Y" is exactly the kind of thing that can get everyone killed. You either have multi-lateral collective security or you do not. You either make security guarantees to scare Putin from attacking Ukraine or he does. You either tell Xi that he will not violently take over another South Asian democracy or he will.