iPhone location stuck in US after moving to Netherlands

What's is the Apple ID country that it is associated with?

Do not do it using your iPhone.

Change your Apple ID country online

1. Sign in to appleid.apple.com.
2. Tap or click Personal Information.
3. Tap or click Country/Region.
4. Follow the onscreen instructions. You must enter a valid payment method for your new country or region.

What to do before you change your country

• Spend any remaining balance in your Apple ID. If you’re not sure whether you have a balance, check your Apple Account balance.
• Cancel any subscriptions that block a country or region change, and wait until the end of the subscription period. 
• Wait for any memberships, pre-orders, film rentals or Season Passes to end, and wait for any pending store credit refunds to be processed. You can cancel a pre-order.
• Make sure you have a valid payment method for your new country or region. See what payment methods you can use.
• Re-download your apps, music, films, TV programmes and books on any devices you might use to play or read them in the future. Some types of content may not be available in your new country or region. Find out what types of content and services are available in your new country or region.
• After you've updated your Apple ID billing address and payment method, you can upgrade your iCloud+ plan using the pricing in your new country or region.