I don't know why anyone should be surprised by any of this as it all part of strategic planning and makes military sense.
The morality of it is another issue, but the US is in a powerful position and intends to remain there. I think any other country that was in a similar position could well act much the same and in some cases be even more willing to destroy perceived enemies.
I am not in favour of using nuclear weapons except as a last resort like ending WWll, but I don't think their use in the Middle East would result in WWlll - most likely a quick victory by taking out the bulk of your opponents in one swoop, and leaving them nothing to retaliate with.
I don't think other countries would retaliate on behalf of the losers, partly because they are not really interested in doing so and partly because they know they would be wiped from the face of the Earth if they did launch an attack.
