We spoke at length with the Team USA soccer legend just hours after Messi confirmed he'll play for Miami's MLS squad in 2023 ... and Lalas said the move is a tectonic-plate-shifting one for the sport in America.

He told us he expects it to attract millions more to the game in the States -- and raise the MLS' profile significantly.

He also, though, predicted it could alter the fabric of Inter Miami tremendously ... telling us he's envisioning Messi recruiting some big names to the team -- and turning it into a villain-like superpower in the near future.

"We're already seeing incredible names now being linked to coming to Inter Miami," Lalas said. "It's almost as if they're in the process of potentially creating this MLS super club Death Star, and the hate-watching is going to be absolutely epic!"

Lalas said if it does, indeed, take that turn ... he's anticipating it to create some serious rivalries in the U.S. league -- which would be a big boon for fans here in the States.

"I know if I was on another team -- a less sexy team, for example -- and Miami was doing all of this," he said, "and one of the greatest to ever play is there, I would want to kick his ass."

But, Lalas did offer fans to proceed somewhat cautiously at least initially ... explaining to us that, currently, the Inter Miami roster is not exactly the best -- which could lead to some early frustrations for Messi.

Then again, he told us he's fully ready to see flashes of brilliance from Messi ... despite his roster's limitations and his 35-year-old age.