The US owns and regulates the frequencies TV and radio are broadcast on. The Internet is not the same. If the threat of foreign propaganda is the purpose, why can I download the official RT (Russia Today, government run propaganda outlet) app in the Play Store? If the US is worried about a foreign government spreading propaganda, why are they targeting the popular social media app that could theoretically (but no evidence it's been done yet) be used for propaganda, instead of the actual Russian propaganda app? Hell I can download the south china morning post right from the Play store, straight Chinese propaganda! There are also dozens of Chinese and other foreign adversary run social media platforms, and other apps that could "micro target political messaging campaigns" available. So why did the US Congress single out one single app for punishment?
Money. The problem isn't propaganda. The problem is money. The problem is tik Tok is or is on the course to be more popular than our American social media platforms. The problem is American firms are being outcompeted in the marketplace, and the government is stepping in to protect the American data mining market. The problem is young people are trading their data for tik toks, instead of giving that data over to be sold to us advertising networks in exchange for YouTube shorts and Instagram stories. If the problem was propaganda, the US would go after propaganda. If the problem is just a Chinese company offers a better product than US companies, then there's no reason to draft nuanced legislation that goes after all potential foreign influence vectors, you just ban the one app that is hurting the share price of your donors.