When I go to the main page of Google Contacts, contacts.google.com, I see some U.S. phone numbers in the (123) 456-7890 format, and others in the +11234567890 format. (I prefer the former format, FWIW.)
When I go to the editing interface for individual contacts, I can confirm that the numbers are input exactly the same.
So, for the life of me, I can't figure out why these numbers vary in how they display.
Anyone have any insights?