The Left has been trying to take control of America for about the last 100 years. Shifted into high gear in the '60s. Have made great strides since then, sadly.
Can't see them all of a sudden "becoming civilized" or accepting American values. I doubt anything will deter them... except a civil war where millions of them (and us Americans) are killed. Would like to be wrong about that.
Lots of Americans have guns. Not too many Lefties have them, having been morally/control opposed to them. Maybe they'll take that into consideration and think better of what they do.
Communism only looks good when society is totally capitalistic because the socialists need capitalists money. The more socialist, like the USA, a country becomes the less enthusiasm there is for communism because people realize to progress any further means more goes to the government and less to the people.