None of them pose much of a threat to bitcoin. I'm not going to say that bitcoin is immune to things like widespread government banning, or extreme taxation, but the longer bitcoin is around, the safer it gets.

I don't know when it becomes an unstoppable force, maybe it already has, who knows. I do however believe at a certain point it becomes too large for anyone to do anything to even slow it down, and if we aren't there yet, we aren't far away.