It is the World Cup - but it is only the womens' World Cup. I think the lack of buzz is because the womens' game is still not taken as seriously as it should be. I've heard commentators say several times throughout the tournament that this or that country's womens' team does not get much support and/or money from their federations.

There is also the fact that media attention in the US, not too focused on soccer to begin with, is cyclical in the sense that the big showcase tournaments - the World Cup and the Olympics - are each four years apart, but follow each other (the Olympics are next year). So in effect there are always two years of no major action, and the attention wanders elsewhere.

On the other hand, there is the huge factor that there is hardly anything else happening in sports right now...