Sounds good on paper, sure, but ultimately it will end up being a predictable bureaucratic mess, causing more harm than good:
a) The mandatory 'open' standard that gets produced will end up being designed by committees of management teams from 6-7 major companies, each with their own list of feature requests and no central 'vision'.
b) A lack of a cohesive strategy and (critically) a lack of real incentives by the members to partake will result in endless delays, slow moving technological progress, layers of old cruft that never gets removed, and toxic political infighting causing confusion among vendors.
c) The standard ends up being so complex and involved that it isolates other small/medium sized players (or large foreign players) from joining in, eliminating the 'openness' the original regulation envisioned and crippling competition.
d) Ultimately reduces the ability for developers to get paid via monetization and grow via capital investments in the US, as non-regulated open-source projects (or foreign private apps) gain a major advantage of not having to be forced to use the standard. Cannibalizing the market the big players spent so much time/money building.
It's not just about good intentions and spotting a tough problem, it's about whether they can realistically and effectively achieve the end goals...
TLDR: open-source and the global nature of technology, lack of incentives, design by committee, regulatory agencies staffed by the very same companies it's regulating, etc, etc will result in the crippling of innovation and harm the quality of chat apps in the US.
The takeaway from the USB success is not to design a new protocol by committee, rather pick a mature open standard - for textual chats there are several mature ones.
Could we assume that we all understand the downside of regulations ? but that we still suggest some when the market fall into a bad optimum (bad for the consumer).
If you don't agree that the market is stuck in a bad place, fine you can argue that.