For GUAM as a State of the United States, example:
Test Guam US First Test Guam US Last
123 Somewhere
Yigo, GU 96929
United States

United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Media MailŪ) $21.39
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Standard PostŪ (4 - 7 days)) $24.38
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Priority Mail Express™ Flat Rate Envelope (Array)) $30.64
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Priority Mail Express™ Legal Flat Rate Envelope (Array)) $30.64
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Priority Mail Express™ (Array)) $41.85
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (First-Class Mail Large Envelope (2 - 5 days)) $44.00
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (First-Class Mail Parcel (2 - 5 days)) $44.00
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Priority Mail Express™ Flat Rate Boxes (Array)) $55.60
For GUAM as a Country:
Test Guam First Test Guam Last
123 Somewhere
Yigo, 96929
Yigo, Guam
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Media MailŪ) $21.39
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Standard PostŪ (4 - 7 days)) $24.38
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Priority Mail Express™ Flat Rate Envelope (Array)) $30.64
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Priority Mail Express™ Legal Flat Rate Envelope (Array)) $30.64
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Priority Mail Express™ (Array)) $41.85
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (First-Class Mail Large Envelope (2 - 5 days)) $44.00
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (First-Class Mail Parcel (2 - 5 days)) $44.00
United States Postal Service (1 Boxes) (0 lbs, 4 oz) (Priority Mail Express™ Flat Rate Boxes (Array)) $55.60
Other than I am going to have to check later as to why I see Array on some of the days when I have time to check my settings and such ... it seems to be working for both ...

If yours is still not working, please turn on the Debug to Logs and Zip your logs and attach them to your next post ...