If the US ban reasons are valid and Google is forced to remove it from the store for those reasons, then sideloading TikTok would be this exact situation I'm describing.
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Let me restate it like this. Company A wants access to iOS app market. Their app does X, Y, and Z. Z is frowned upon but X and Y are pretty valuable. In a world with no rules (i.e. sideloading), they'll do X, Y, and Z and consumers will have to put up with Z. In a world with rules (i.e. App Store), they will have to omit Z even though it's good for business because that's the only way they can do business in X and Y.
Also, sideloading doesn’t necessarily mean there’s no access controls or permissions on iOS any more. Though Apple might have to step up security and fixore bugs.