Soccer has grown a tremendous amount in the United States in the last 30 years.
I don't think most people understand how dead it was in this country. Even when we hosted the 1994 World Cup and MLS began, most people thought it would never work. It's made great strides.
That said, soccer is still prohibitively expensive at the youth level in this country. So unless those costs start coming down, I don't think it will ever get to the point where it's a consistent powerhouse. At least when competing with other countries.
This is a major step though -- being on HBO and popular cable channels like TNT and TBS.