Grist, you might think, for both sides in the Soccer Wars comes from this Economist poll, which reports that 55% of Americans have no interest whatsoever in the World Cup. See! Soccer will never catch on!
Except that 21% of Americans say they are following the tournament at least somewhat closely. My back of an envelope calculations, then, suggest that twice as many Americans are interested in the World Cup as believe Elvis is still alive.
That's an awfully large number of people.
(What's more, I'd guess that a poll in other "more developed" footballing countries would find that a third of the population, and perhaps more, has no interest in the World Cup either.)
Furthermore, American soccer fans are firmly within the international mainstream. They too massively overestimate* their team's chances of success:
*Poll conducted before the US-Algeria match.