Whereas Tom Cruise is the prototypical American, showing only the upper teeth:
Quoth the talking head: Americans tend to misinterpret the English smile as a grimace, indicating "submission but without joy". This might explain much about the special relationship if it were true, but is it? Charles looks to be in anguish to me, as he usually does (Google "Prince Charles smile" if you don't believe me). Actually, though, I don't think either of the above smiles is real, although Cruise is certainly better at faking it.
But what do I know, prosopagnosiac as I am? On which note I have to say that the McGurk Effect, which they went on to discuss, passed me by entirely. Try it yourself: