To be fair, he did specifically ask about the US, but yes, it is amazing how many Americans are unaware that the age of consent is not a universal.
I remember on a LBGT newsgroup my late wife and I used to frequent, the resident homophobic troll got quite hysterical when we told him the gay AoC in the UK was 16... how dared we try to put over such a lie, everyone knew it was 21 everywhere!