re: If nukes are ever dropped on America, what will be hit first?

Depends on who's nuking us.

If it's a peer or near-peer attacking us (Russia, China, India, Pakistan) they'd probably target our Command and Control capabilities so we couldn't strike back so the facilities in the Plains and important military and political targets. That's not going to happen.

If it's a terrorist group I'd imagine the target would matter less (any detonation on US soil would be a win for them) and therefore it would be less predictable. I'd imagine it would be a city on the coasts or near a border as smuggling a nuke to Chicago or St Louis would be much more difficult then say, detonating it at a port in Miami or LA.

I think the second is a more likely scenario, it doesn't keep me awake at night or anything but it wouldn't surprise me if it happened. Between Pakistan's general instability and the possible (probable) loss in accountability of Soviet nukes in the early 90s it could potentially happen.