Ok so if intelligence reports claim there's a risk of a coordinated attack

The US is the only nuclear armed country with a history of actually using it. I'm a LOT more scared of the US doing the coordinated attack on someone than I am of the thought of any of the other nuclear armed countries striking first.

Also implying I trust literally anything the US intelligence machine ever says ever.

what do you think the US should do to defend itself?

Boring answer: Not fucking use nuclear weapons, that's for sure. Diplomacy should be enough.

Honest answer: I literally don't care about the US government's "right" to "defend" itself literally at all. As far as the innocent people who actually live here, we will respond in the only way that our government has planned for us in any disaster scenario: get sacrificed to maintain continuity of government and capitalist power.