Google, fb, Twitter doesn't comply with internet security law in China, which requires servers in China and content regulation. The same law applies to everyone. If you follow it by the letter, you can operate. Case in point, Apple iCloud, Amazon, Microsoft azure etc. Yes the law itself is highly controversial. I for one would want this law changed. But at least the path for market access is documented. In tiktok case, it didn't break any existing us laws. It has an American office and hires Americans to do security and content monitoring. All data is stored on US soil. It promised to let outside review of data practices and how the algorithm works. There is no clearly spelled out procedure to follow to be allowed operating in the US. I am sure tiktok people are searching in the air for ideas to get themselves allowed to operate. I think thats the difference between fb in China and tiktok in the US.