No player is going to want to move to Mexico. They would lose every player once they are eligible for free agency. They would have a nightmarish time signing free agents. Mexico City and London would be horrendous for the players.
I think the idea is that the teams would only play games at those sites and not actually live there. So in London, the team offices and practice facilities would be in New York for example. They’d play 2 games in the US and then have 2 home games in London. In an 18 game schedule, that means you only spend 9 weeks in London out of the year