One view (at first endorsed by Andrew Sullivan, though later changed to “see[ing] the deeper point”):
I think that the United States and the West generally, we have to educate ourselves more effectively on Islam. And one of the points I want to make is, is that if you actually took the number of Muslims Americans, we’d be one of the largest Muslim countries in the world. And so there’s got to be a better dialogue and a better understanding between the two peoples.
Another view. I haven’t independently checked the data, but I’m pretty sure that with about 5 to 7 million Muslims [UPDATE: that seems to be one of the higher-end estimates], we don’t even make the list. Certainly “one of the largest” is subjective enough to leave some wiggle room, but not that much wiggle room. If we’re one of the largest, then Burkina Faso (with more Muslims than there are in America, and according to Wikipedia, #30 on the list) must be a veritable giant of a Muslim country.
A small matter, but it struck me as worth noting.