Former England captain David Beckham kicked the domestic league into another gear two decades ago when he signed with LA Galaxy, and Golden Boot contender Messi has had his own profound impact three years after signing for the Beckham-owned MLS side.
His heroics on the sport's biggest stage, including two last-gasp assists to get Argentina past England in the semi-final on Wednesday, stand to make him an even bigger draw when he returns to his club.
"None of us in the league understood what Messi was when he was playing at Barcelona, other than as fans," said MLS Commissioner Don Garber.
"The fact that he would have a right-footed cross at the last moment — see, I even know what that is — and be able to win a game in front of the world and be in the final, and then take off his Argentina jersey and put on an MLS jersey. I never dreamed that that could happen."
Garber told Reuters last month that he views the quadrennial showpiece tournament on home soil as a launchpad for a new era in the U.S. league.
That growth may be helped by the arrival of Orlando City's recently acquired forward Antoine Griezmann, the all-time leading scorer for LaLiga club Atletico Madrid, who said the level of competition at MLS is above what it was in years past.
"The World Cup also helps so all kinds of American kids can enjoy soccer and want to start kicking a ball," he said. "Hopefully, we can put on a show in the stadiums to make kids want to play soccer."