Time to read the small print.  NATO was intended to tie the USA, and Canada, into a defense of Western Europe.  I am not certain it requires the European signatories to defend North America.  Second, they are "mutual defense provisions".  What are we doing to help defend the USA against a missile attack?  Anything?  No huh?  We are not being very mutual, even when offered the opportunity to be so.  So if missiles are launched at the USA, I am sure we will rush to help, after the attack is over.  They might even say thank you.  We will do squat during the attack and have equipped ourselves to do nothing but squat during the attack.  But you want to insist that the USA has to defend us?  I am at a loss as how to express my contempt for this opinion and stay within the bounds of good behavior required of a participant (though I think that was a pretty good effort).