On Facebook, I'm honestly not concerned. Just look at the last few years where facebook.com fades into irrelevance (with IG not that far behind) while TikTok has surged and honestly poses an existential threat to FB's business (IMHO). That problem, if you consider it one, will take care of it self.
On Google, I'm not concerned either. Google dominates search because it's quite simply better than everyone else. Using another search engine is easy. Making that alternative search engine obviously isn't but the modern doctrine of US antitrust is not to protect competitors from competition; it's to protect consumers from anticompetitive behaviour. You can argue all sorts of anticompetitive behaviour. I'm not yet convinced by any of it.
As an aside, it'd be foolish to engage in killing our own golden geese while Chinese competitors rise in influence, especially given the deep ties between Chinese companies and the CCP and the fact that the Chinese market is typically barred to competitors while Western markets aren't barred to Chinese companies.
And then there's Amazon. To me, Amazon is the clearest case for government action for it's effective monopoly over distribution. Yes you can sell stuff on your own website. You can ship physical products. But in doing so you cannot compete with Amazon's price-points, speed and overall logistics.
On this the Chinese too have had an advantage by taking advantage of the postage union in a way that a domestic supplier cannot.
I'm not sure this has yet reached the level that warrants government action. When it does I'm honestly not sure what we'd even do.
I wonder how your extension will handle scenarios with unclean data, however. What if the state labels were irregular?