I mentioned to Grahame Jones that traveling support for MLS teams is slowly changing. Basically, the distances between teams are so considerable, that the support is very one-sided. It's lacking that fan oppositional energy that makes many matches abroad really riveting.
But as fans grow up with a team, (say, Kansas City), and then move on (perhaps to New York), they're more likely to remain loyal to whatever team they first supported and turn out to do so when that team visits.
For example, I have a group of friends here who are from Chicago, and they never miss a Cubs game when they're in town here in Los Angeles. They're not alone. Cubs fans practically make up half of the stadium for those games. Well, the other day, there was a new Chicago expat in the group, someone studying at USC for a grad degree. My friends were talking to him about adding him to the ticket count for the Cubs game.
"I don't know," he responded. "I'm short on cash right now, and I'd really rather save the money for when the Fire come to town."
He explained to the other Chicagoeans that the Fire was the team he'd followed for years, since they were formed.
"It was amazing," he declared. "First year in the league and they won the championship. I was so pumped."
By the time the meal was finished, he'd convinced half the group to join him at the Fire game, just in a show of Chicago solidarity.
It will take time, but that's part of the soccer diaspora. A Revs fan in Ohio. A Colorado fan in Chicago. Bit by bit, especially if they form groups to go to games together, away fans will make more of an impact on games.