How can I change my Apple ID region from Asia to U.S My Apple ID region is Indonesia but I wanted to change it cause I can't download some app on the Indonesian store
I think this page can help you.
But I'll explain it here too.

On your device, tap Settings > iTunes &amp; App Store.
Tap your Apple ID. 
If you're not signed in, sign in with the Apple ID and password that you use with the iTunes Store.
Tap View Apple ID.

If prompted, enter your password again.
    Tap Country/Region. Learn what to do if you can't change your country.
    Tap Change Country or Region.
    Tap your new country, then tap Next.
    Review the Terms and Conditions and Apple Privacy Policy, then tap Agree if you agree to the terms and conditions.
    In the prompt that appears, tap Agree.
    Select a payment method and enter your payment information. Learn more about how to change or remove your Apple ID payment information. 
    Enter your billing address and tap Next.

Your Apple ID country updates for all of your Apple services on all of your Apple products.

Open iTunes.
If you’re not signed in, sign in with your Apple ID.
From the menu bar at the top of your computer screen or at the top of the iTunes window, choose Account > View My Account.
    If you’re using Windows and can’t see the menu bar, learn how to turn it on.
    Enter your password, then press the Return or Enter key on your keyboard, or click View Account.

On the Account Information page:

To the right of Country/Region, click "Change Country or Region."
    From the "Select a country or region" menu, select your new country. Learn what to do if you can't change your country.
    Click Change.
    On the Welcome to the iTunes Store page, click Continue.
    Review the Terms and Conditions and Apple Privacy Policy. If you agree, select “I have read and agree to these terms and conditions.”
    Click Agree.
    Enter your payment method. Learn more about how to change or remove your Apple ID payment information. 
    Enter your billing address. 
    Click Continue.