The biggest problem, really, is that the US owners are competing with three huge American sports - American football, basketball, and (more limited) ice hockey. Both at the professional level and the college level. There is a reason the MLS plays when it does.
The most viable money maker would probably be a longer summer UEFA World championship held in the US over 6 weeks. It would be a technical "real competition" but serve as a pre-season tournament for the European teams. It also gives a playoff, which Americans think is necessary to have a "real" champion.
Football (the American soccer) just isn't anything but a class-statement in the US, and won't get the same support as American sports (people visit international Rugby matches, too, but don't really follow it. Lacrosse? Don't get me started.)
But there is no sport in the US that has a true league champion - and that is what everyone should be worried about - the desire American owners have for a play-off system.