IMO, there are plenty of good reasons not to launch.
Imagine you are a communist dictator. Would you rather have the US bombed to rubble or would you rather take over and expand your empire by annexing the US.
I believe the latter is preferable (and is happening). Bombing to rubble is a last resort, a desperate move that you would make if you felt it was your only option to protect yourself. That said, there is no guarantee that the various dictators of the world are capable of thinking logically. Illogical and irrational people make stupid decisions all the time. (This is why we need to keep democrats who are purely emotion-driven out of office and away from any sort of power.)
It is not possible to “take over and annex” the US.
Nobody even dreams of such nonsense.