Fifa can't mandate MLS to do anything due to the anti-trust laws in the US.
Right. I get that. I'm saying FIFA also wouldn't be able to do anything about an "unsanctioned" (and non-USSF licensed) "Rival Soccer League" for the same reason. They'd sit idly by and hope that it succeeded to the point where it forced the sanctioned / USSF-licensed league (MLS) on to the world calendar like the rest of the world, which they'd want because the US/Canada have top 20 economies but are spending like Wrexham levels, not like Man City levels.
And I don't think the lack of USSF-license would be prohibitive to the rival league. The USSF could say "anyone who plays in this league can't play on the US National Team." But the USMNT talent pool is TOO GOOD for MLS now, unless they're 18-21 and haven't been sold to a better league yet, or they're 30+ and coming to MLS for a "homecoming/semi-retirement."
It would simply be a competition of which style the American fan wants more: Open League, 60-120 teams, PRO/REL vs Closed League, 30 teams, no PRO/REL.
The other leagues HAD their "Rivalry days" and is beyond that while soccer isn't yet. Baseball did it in the 1880s and the AL/NL emerged with the agreement for the World Series; A mild version in the late 50s early 60s with the PCL before the Dodgers moved to LA and the threat of the CBL from New York. Basketball and football and hockey were the late 60s and early 70s.
The "end game" would not be to "usurp" but to force change, as MLB, NFL, NHL and NBA expanded/merged/absorbed and extended their borders and took the best elements of both leagues.
That's really what it would be about: I think that a rival soccer league would have a chance to change MLS based on numbers. An open, massive league operating on the world system would be like "Okay, this can work here..." So MLS could change to kill the rival league by converting to that system and inviting the top teams of the rival league (and leave the rest to die).
The AHL has teams like the San Jose Barracuda and the Calgary Wranglers that don't draw flies and the NHL teams don't care about that.
20 years ago, it would make sense, but not today.
Absolutely. The AHL doesn't serve the fans need for hockey as it's primary focus. It serves the NHL as a development league. The teams aren't in places the NHL would explore expansion, they're in places close to their parents, or where existing arenas lower operations costs to the parent.