Well if he had became a national of the USA as well as the UK he would still be liable to pay both as you are taxed in the US as a citizens while you get taxed in the UK as a resident.
So it depends on his status while resident in America.
I don't see how Jim is going to do anything else but the most vapid surface level work, he knows he's on the career death spiral and it's not due to a lack of intrest in the subject from the people but change in tastes in how they consume the subject matter.
So frankly would Jim put in anything more than the bear minimum.