If the sitting President, for whatever reason, became royally pissed off at you individually, would you be nervous about it? What about other elected officials? Non-US dopers, what about the leaders of your countries: would Gordon Brown (or Queen Elizabeth) inhabit your nightmares?
I wouldn’t be too worried if the president were mad at me, but he could probably do something to screw with my passport so that I’d have to return to the US and face the wrath of the IRS or whatever.
On the other hand, if I were sitting right in the Texas governor’s mansion and Rick Perry came storming all wrathful-like, I wouldn’t hesitate to laugh in his face. (Now with the Comptroller or the Lieutenant Governor I might tread a little more carefully . . .)
ETA: Why yes, I was thinking about John McCain just now, why do you ask?