This would be an argument in favour of preventing countries from developing any deterrent at any time, because it would make them easier to invade. It presumes, firstly, that it would be a good thing for the United States to be able to invade countries that do things it does not like at will, and secondly that it assumes that deterrence will not deter the initial invasion in the first place.  The main reason why great powers involve themselves in wars, is because many smaller countries are not able to fight off larger ones using their own resources and so the great power expects an easy victory assuming it can avoid intervention by other great powers. Jammu and Kashmir could not stand up to the Indian army in 1947 and Kuwait could not stand up to Iraq; Georgian was unable to mount armed resistance against a Russian incursion and neither was Chechnya.  Nuclear Weapons are a great equalizer, and if one consequence of Iran developing Nuclear weapons is that all of her neighbours do so as well, then war will become far less likely, and US intervention will become unnecessary. As a consequence, in the long-run, Nuclear proliferation is a self-correcting problem.