Yeh I may well be underestimating the sheer financial prize offered right now by tapping into white guys in Wisconsin or wherever, as opposed to some truly global market that's more future potential. It's easy to get caught up in the global nature of European football when (for example from my experience) you can watch the premier league in a bar in Dar Es Salaam, forgetting that these fans are worth fuck all in broadcasting/advertising revenue in the big picture.
That's a really interesting point about the Mexican league. I suppose you could imagine, years into the future, a proper inter-American (i.e. the whole Americas) club competition getting big audiences.
Funny story about immigrants to the US and football, since I've nowhere else to share it. My wife is from Miami but her family are from the Caribbean and love football, to such an extent her brother is called Edson (as in, Pele's real name) and her cousin Diego. She was telling some German bloke this one time and he was like "do you have another cousin called Klinsmann?" As if Klinsmann is the third name on that list? Talk about German arrogance.