AtomKraft
If Uncle Sam wants to interfere with a country and considers it important enough to do so, there are a number or ways to do so. An open invasion is nice and impressive but an internal uprising has its merits too.
Plus the good old MAD doctrine functions only in large scale - a country with two or three or even 10 weapons and no suitable long range delivery vehicles has little chance against an army with the nuclear arsenal the size of the US.