I don't know what Congress has said but there absolutely is evidence that TikTok has been used to spy on users for political reasons. A US based engineer claims that he saw evidence that Hong Kong protestors were spied on in 2018 at the behest of a special committee representing the CCP's interests within ByteDance. This is not surprising, most major corporations within China maintain a special committee representing the government's interests to company executives

https://www.aljazeera.com/economy/2023/6/7/china-spied-on-ho...