because contrary to what you believe, many Chinese looked up to aspects of the US.
I'd guess it's a very small percentage.
to directly answer your question, if you think this is a war of ideology, this move doesn't do the US any favors, regardless of how necessary or justified it is
Fine.
Here are 3 geopoltical issues that are way bigger than TikTok banning: Hong Kong, Taiwan, disputed islands on South China sea with Vietnam and Philippines. These issues evoke much stronger nationalism.
A large portion of Chineses probably already look at US as very bad guy regarding these 3 geopolitical issues already. Trying to turn Chinese's regular person to be positive by not banning TikTok is not worth it.
It's not like "oh yeah, I like US now because they don't ban tiktok, even though they try to help taiwan, hong kong, and etc. It's fine. TikTok is way more important here." Probably said no Chinese person ever.