With the sort of detailed personal profile a social media app has on you, they could target your specific beliefs, religious convictions, sexual preferences, political affiliation, fears, interests, desires, etc. to manipulate your opinion in their interests. Doing this on a population-wide scale is what social media platforms are all about (i.e. targeted advertising). It’s wise to be concerned about an adversary having such a tool at its disposal. And this is true for all countries, not just the US.