Late to the party as usual. I too am troubled by the clear evidence that the combination of larger headed metal drivers with the ever improving balls have led to longer and straighter drives. This has led to older courses losing a significant portion of their challenge, at least for players at the highest level. It has also led to an increase in the length of courses and attendant increases in costs and the time needed to play. But regardless of your view about the USGA, I think we are all overestimating its ability to dictate changes in the ball.
The USGA has no inherent right to govern the game. It, along with the R&A assumed that role early in the development of the game when a few leading clubs formed the organization to bring some order to the game. They have maintained that position because all of those involved have consented to their role. Notably, when Karsten challenged that role with his suit challenging the square grooves rule, the USGA blinked. Since then, despite building a large litigation war chest, the USGA has not "taken on" any major manufacturer.
Putting aside any litigation, assume the USGA changes the rules either via scaling back the ball or via bifurcation. Assume further that the equipment manufacturers tell the touring pros that because the pros are no longer the model for amateurs due to their inability to market increased distance, the endorsement payments will be cut significantly. It would not be surprising for the PGA tour to adopt its own equipment rules. Their only risk would be a ban at the US Open and maybe the British Open. The counter risk for the governing bodies would be the tour sponsoring counter tourney's and declaring them "majors".
Under that scenario, who would the average player/fan follow.? I suggest that amateur golf has a very small following while the pros are viewed as the standard setters. Currently, only a very small percentage of golfers really play by the Rules of Golf. So, putting aside all the other issues regarding bifurcation involving high level amateurs, if economics caused the touring pros to defy the USGA, the USGA runs the risk of becoming irrelevant in a short time. I suggest that the USGA is likely considering this risk which may explain why it periodically floats trial balloons and doesn't follow through.
This is not to belittle the many arguments relating to the impact of increased distance on classical architecture. Similarly, the sustainability issue is not impacted by these observations. It is merely to suggest that these arguments, valid though they may be, are likely to fail in the face of economic considerations. If one believes that the touring pros (who are paid by the manufacturers) and the manufacturers will go along, then the other arguments become critical. Similarly, if one is convinced that the golfing public will follow the USGA and deem decisions made by the pros to be irrelevant, then further discussion of the merits may bear fruit. But I, for one, am dubious.