You are putting the horse in front of the cart. Companies pay TT to advertise to get exposure for their products, not out of charity.
If a ban takes place but everyone in America still uses TT anyways (just look at prohibition and current US illegal drug use statistics to see how well bans work to get people to give up on things they want to do), American companies will become even more uncompetitive in their own markets compared to foreign rivals who do advertise on TT.
The only way America can actually do serious damage to Bytedance is if it places secondary sanctions in place on top of a ban. Secondary sanctions are nothing like a ban, and as far as I am aware, are not in the bill and on the cards, in the short term at least. If America is loony toon enough to try secondary sanctions, then it will be full spectrum economic nuclear war with China as China absolutely will not allow such a precedent to be set unopposed.