Another reason could be: many are not sympathetic to the America's claims that these foreign platforms are at the whims of a country it is at odds with and which have repeatedly demonstrated covert abilities to change American's perception.

Speaking with some younger American co-workers in the past, their suspicion/hatred of their own country is astounding to see and it seems to have coincidentally begun after TikTok entered US market a few months before US elections.

So the worry seems to be that young American voters exposed to a foreign social platform will influence upcoming elections. I do not think this is far fetched as multiple countries have come out to expose various tactics by certain countries to influence perception.