Speaking to Al Jazeera TV, the controversial Swiss claimed that despite the league being formed almost 20 years ago, it is yet to make a significant impact on American sports fanatics.
"Don't forget that soccer — as they call football there — is the most popular game with the youth," Blatter said. "It's not American football or baseball; it is soccer. But there is no very strong professional league. They only have MLS, they do not have these professional leagues that are recognised by the American society.
"I thought it was a question of time when they had the World Cup in 1994, but now we are in 2012 - it’s been 18 years - it should have been done now. But they are still struggling."Statistics show, however, that MLS is ranked third in terms of attendance at American sporting events, with an average of 18,807 fans per game.
But TV audiences are dwindling, with David Beckham's final game for LA Galaxy drawing far fewer viewers than any regular-season game in any top American sport.
Blatter has previously suggested ways in which MLS can improve its apeal, and in 2009 he called for league chiefs to rearrange the calendar so it falls in line with the major European competitors.
"They have to play and adapt themselves to the international calendar," Blatter said at the time. "If they do that, they can have success. I spoke about this 10 years ago when I was still secretary general and nothing has changed in the US."
MLS Commissioner Don Garber responded by explaining that the league is still working on having each team play in a football-specific arena. Currently, six of the 19 teams still share their stadiums with other sports franchises.