I’m Norwegian so the US geography was not the most important thing to learn at school, most of us learn (some of) it later in life anyway, b/c US is the most important country in the western world, and the most interesting one to follow news and such, so for many outside the US (especially in Europe), it is generally the country we know most of, except for our own country. And all the films and TV series from the US contributes a lot.
But I think the reason why I was wrong on the actual number of states, is that, at least here in Norway, and probably in other European countries too, we tend to say that this or that country is the 51 state, b/c we (or other countries and politicians) follow and/or support the US foreign policy automatically instead of deciding our own foreign policy. And this issue is not necessarily related to the fact that we have many different opinions of the US foreign policy.