A big difference between the NFL and European soccer is that there's little correlation in the NFL between being the richest team and the best team. The Cowboys are probably the richest team and they've been mostly mediocre for decades. Same with the Giants. Meanwhile last year's two super bowl teams were two of the league's smaller markets in Kansas City and Tampa, and one of its historically most successful and popular teams is Green Bay, by far the smallest market in the league. And the NFL, of course, has revenue sharing and a salary cap and a draft to maintain competitive balance.
A lot of this has played out in college football with conference realignment and the creation of the playoff in the past couple of decades. It's been really rough on the old Big East, and the SWAC schools who got left out of the Big 12, and a bunch of others. Many of those affected programs have suffered, and a lot of traditional rivalries have been lost (Oklahoma-Nebraska, for example). But it has hardly diminished interest in college football generally. College football is bigger than ever.
I would love some kind of salary cap + revenue sharing system that created competitive balance in Europe. But that's never going to happen.
I think you're missing my point. I'm not talking about competitive balance; I'm not a pipe dreamer who believes that a revenue sharing system is possible or even worthwhile in European football. I'm talking about fundamental revisions to the nature of the competition itself. All of the movement you've just described in college football hasn't fundamentally altered the nature of how college football works: teams play a conference schedule and a few non-conference games, and the best teams go to bowls and/or the playoffs, with a chance to compete for the national championship. If Alabama and Clemson and Ohio State and a handful of other teams decided they were too good for the NCAA system and broke off to make their own football Super League, that league would be interesting, and it would probably generate a lot of money...but what exactly would this Super League *be*? They wouldn't be playing for the "national championship". They'd be playing for the Super League title, nothing more. There wouldn't be any romance or history or tradition in that. And at a certain point, after LSU or Oregon or whomever went 0-11 several seasons in a row and stopped being able to recruit good players any more, we'd start wondering why they were included in the Super League in the first place, and if they were able to join because they happened to be good at a certain moment in history which is no longer particularly relevant to the league's raison d'etre.
In European football's current structure, it is theoretically possible for any club in any league to become the Champions of Europe, just as it's theoretically possible for Vanderbilt or Rutgers or Kansas to win the national college football title. Manchester City were in the third tier of English football as recently as 22 years ago. They had obvious financial help in getting where they are today, but fundamentally they got to where they are because they kept winning football matches. And much of the current system's legitimacy derives from this romantic notion that if you win enough matches, you can ascend to the very top of the European pyramid. (Why do you think the Football Manager series of computer games is so popular?) As soon as you close the system so that this is no longer the case, and there exists a glass ceiling through which your club may not pass, the nature of the system fundamentally changes. And I don't think the nature of that new system will endear any of the seceding clubs to any fans of the have-nots which the Super League would in theory be permanently leaving behind. Certainly, the winners of this Super League could no longer legitimately call themselves "European Champions". And when Arsenal and Tottenham or whomever else finishes bottom of the Super League for the Xth year in a row, playing a series of increasingly meaningless matches every year from January onward (under no threat of relegation), their existence within the Super League will likely raise questions about the entire enterprise.
I think a Super League can work - if it encompasses promotion and relegation. That structure would still be incredibly divisive, particularly if it caused clubs to exit their domestic leagues (although a case can probably be made that big clubs will probably have enough players to compete both domestically and in Europe, perhaps with separate managers and mostly separate squads for each competition). But if it is a closed system, it may come to feel too much like a glorified series of exhibitions than a competition worthy of the talent it encompasses. In particular, are fans of teams in the bottom half - or bottom quarter - of the Super League table really going to take kindly to seeing their clubs lose all the time? The Champions League is by definition a competition in which winners play other winners. Turn some of those regular winners into regular losers, what do you think you're going to end up with?