That ship has not sailed - it can still get a lot worse. The football world still revolves to a large extent around European club football. But we've lost FIFA, who clearly no longer cares much about that - to them their revenue streams lie elsewhere, and they have become the clients of moneyed interests elsewhere. We only conditionally and partly still have UEFA on board - they'll resist any independent encroachment like the ESL because that basically takes their revenue, but at the same time they've proven again and again that they don't really care if their own revenue-producing tournaments go against the interests of the national leagues. They will both continue to try to suck as much as possible of the finite resource of top player game time into international and global tournaments and away from national leagues and cups, because that's where their money is and that's what their patrons want.
The fundamental economic realities of the game have shifted the power and hence the focus - away from the local, and towards the global. The main bulwark keeping things in place is the continued commitment of Europe's dozen or so big clubs to their national leagues - a commitment which the ESL debacle showed to be more than a little shaky. The moment they break out, the European pyramid is dead as anything other than a recruitment system and a second- or third-rate competition. Neither American or mid east owners have any intrinsic attachment to the European club system. The Americans will be attracted by the commercial potential of a closed league, but the mid-east owners will additionally be attracted by the possibility to shift the prestige of top clubs to a more global stage, and by the expansion of international tournaments (both club and national teams) that are more directly relevant to their own home constituencies. Right now, only 2-3 of that dozen clubs are owned by sovereign oil money, if that becomes 6 or 7, we're looking at a very different reality.
So I think it's really quite myopic to think only in terms of how oil money ownership would work for United, in isolation.