As a user and not as a government agent, why should I care? If anything, having a foreign government hoard my data and spy on me is better than the government that actually has jurisdiction over me. If I were posting things critical of my own government I would rather have a foreign government hoard that data than my own government. There's a lot more of a chance that US data hoarding leads to action against US citizens than Chinese data hoarding.
I don't see how this benefits average Americans in any way. This helps the government and corporations.
While I'm not a fan of advertising or marketing in general, brands having a presence on the Fediverse would be great for Fediverse adoption, and sometimes complaining about a brand on social media is needed to get proper customer service in this world of AI and bot controlled customer service channels. I can see this being a good thing, and there are some brands/companies I would likely follow. I already do follow a few who are on Mastodon, such as Framework, Pine64, and Raspberry Pi.