Messi confirmed on Wednesday that he would join the MLS side and play for a club outside Europe for the first time in more than 20 years.
Snaring the record seven-time Ballon d'Or winner is a huge lift for football in the US where it trails the other four major North American men's professional leagues in popularity.
Messi had wanted to go to a club where he could eventually have an ownership stake, a source with knowledge of the negotiations told Reuters this week.
That would see him follow a similar path to that of his new team's co-owner David Beckham, who sent shockwaves through MLS when he joined LA Galaxy in 2007 after exiting Real Madrid, in a deal that gave him the right to a discounted franchise.
Beckham and his wife, Victoria Beckham of the Spice Girls, fitted in with the celebrity-drenched culture of Tinseltown and the move was celebrated as opening a new era for MLS.
Yet Messi's move as a free agent after parting ways with French champions Paris Saint Germain could have greater significance.
"He is the most recognisable and the best player on the planet at the same time," said Eric Wynalda (53), a former US national player and football broadcaster who currently hosts a show on SiriusXM.
"Not only will it be about an attraction, it will also be about getting a chance to see greatness."
The announcement falls short of the biggest shock in North American club football, when late Brazilian great Pele came out of retirement to sign for a little-known US club called the New York Cosmos in 1975.
But with North America set to host the World Cup in three years' time, Messi's arrival coincides with a period of far greater momentum for the sport and could accelerate the popularity of MLS, which has seen steady growth since its inaugural season in 1996.
"(MLS is) not going to become the equivalent of any of the European leagues overnight," said Andrew Zimbalist, a professor at Smith College and co-author of National Pastime: How Americans Play Baseball and the Rest of the World Plays Soccer.
"Most true soccer fans in the United States when they want to see top level competitive soccer are going to tune into European soccer, they're not going to move to MLS. But Messi will have an impact that will begin to change that."
