Contact Apple directly:
Contact Apple for support and service - Apple Support
Apple is aware that users may fraudulently change their region to download apps that may not normally be available to them. Usually this is from users in others countries where the app/service is only available in the US, but I suppose it is true for the reverse as well.
They may have you Factory Reset your device, but that would wipe all data and hopefully you would have a backup. Any apps you have in your backup would be downloaded again from the App Store in the region where you set the device up. Of course, TikTok would not download when the region is the US.