Several points I would like to make:
- Turkey risked it's existence several times for US during cold war, most obvious of which is the cuban missile crises. It is only logical to expect the same.
- If for some reason Russians take the upper hand and get unsolicited access to mediterranean it would be an ENORMOUS strategic loss for NATO
- NATO itself would crumble to pieces if member states see that their safety depends on the US's mood at the time
There are a lot more reasons. These are just the chief ones that come to my mind.
Also there is so much BS talk about nuclear weapons on defence forums (in general) its amazing. Dudes, it has been shown repeatedly using nuclear weapons is a zero-sum game. Even against a non-nuclear state, it would come with an unbearable cost. Turkey does not need nuclear weapons. At least not while NATO exists.