I wonder if there's a third option here...

AFAIK, Facebook still receives government grants leftover from the Dot Com Era, in spite of being a multinational firm with their main offices in Ireland and being worth billions of dollars

What if we treated any firm with, say, 50% or more of their assets outside of the United States as a foreign actor, forbidding them for instance from lobbying, donating to political campaigns, etc. save through the embassy where most of those assets are held, or else assign an ambassador of their own if most assets are still held in the U.S.

I'm not sure how you would set up the finer details, but it seems to me this would allow them to act more or less independently, while keeping them at arm's distance from the U.S. Government...