After a trip to Brazil, my phone cannot correctly format a dialed number without putting a +1 every time

You can change the country format for addresses and phone numbers using https://www.icloud.com

Note: These changes apply only to Contacts on iCloud.com. You must change formatting individually on each of your devices using the Contacts app on iOS and Mac, or Microsoft Outlook on Windows computers. For more information, see the documentation for the apps.

1. Click the Action pop-up menu  in the sidebar, then choose Preferences.
2. Choose a country from the Address Layout menu.
3. To have Contacts automatically add hyphens and other symbols in phone numbers, select “Automatically format phone numbers.” If you want to be able to enter phone numbers in more than one format, don’t select this option.
4. Click Save.

Watch this GIF Below

Please check the Phone Number format stored in your Contact list. There must not be any manually added spaces in between the numbers. However when you enter a phone number iPhone will add spaces, hyphen & parenthesis based on the country code prefixed to the number. That is OK, but do not add manually.

Watch the GIF below