American popular music seems to most people to take up a broader range of styles (folk, country, jazz, rock, middle-of-road pop, r&b, rap, etc.) than Brazilian. Now maybe this is simply ignorance on their part because they know Brazilian popular [1] music *only* though samba and bossa nova. No doubt there is a greater range to it than that. But it is nevertheless true that it is through samba and bossa nova that Brazilian music has become known to the world, and those genres, however interesting, are not varied enough to rival American music on a world stage.
[1] Of course there is Brazilian classical music, too, but the only name in it well-known to most people outside Brazil is Villa-Lobos.