The US has been building military bases around the globe, constantly conducting military exercises and bombing arabic countries as a display of power and provocation against any nation who doesn't ally with them, eventually they will start a 3rd World War.

NATO is based on the assumption the US will win any wars it fights,despite having been defeated by Vietnam and several others. The benefit of joining NATO is "you won't get nuked the US when the war starts". Naturally the neo-libs will mention this also applies in reverse but this is in fact the nature of a world war, you can't stay neutral, you'd either ally yourself with China, North Korea and the others, or you'd ally yourself with the United States and other Nazi-sympathizing nations.

Therefore the benefit of joining NATO is securing your foothold on the winning side when WW3 happens, the downside is becoming a puppet and being required to bomb innocent civilians in Arabic nations, also probably Cuba and Venezuela when the US decides to go there.