It’s you who are missing the point. The officially stated reason for the ban is China’s access to the US users data. This ban doesn’t solve the issue because western platforms/brokers are still able to sell the same data to China.
And yes, US is making a ban out of self-interest. It’s just that interest is purely political and not based on policy or protecting US users.
And China bans all platforms that doesn’t comply with their regulations. We might see it as censorship, but they are fair in how they apply it to everyone and not a single company.