I’d rather go to a chilly game in March than a sweaty, sweltering game in July. Maybe t that’s just me.This would do a severe number to attendance in the northern half of MLS cities.
Too many people don't want to go to games in November, December, May, and April. It's just too cold, rainy, and miserable.
From a purely competitive point of view? Sure; it would work. But this league still makes a lot of its money from gate receipts, and those would take a major hit by not playing in June and July. Come to think of it, when are you doing playoffs in this format? May? So now half the league doesn't get any home gates at all from May-July. It's just a bad idea from a ticketing perspective.
More generally, I think you could figure it out. More home games for southern and western teams in colder months, and vice versa. More (midweek) games in mild months. Etc.
We put a man on the moon, we can figure this out. The benefits of aligning (more or less) with the rest of the world outweigh the downsides, IMO.