1. Log in to the Apple management account
Manage your Apple ID
and log in.
2. Click to enter the country and region to modify
Choose the United States as the country, and then search for a specific address and phone number in the United States on the Internet. Then update your information, and then your account will be able to download foreign software.
3. Log out of the account in the mobile phone and log in again.
When you open the AppStore, your app market will be on the US side.