For factual purposes, the U.S. Registration Bureau has a characterized region called the "Island Areas" which comprises of American Samoa, Guam, the Northern Mariana Islands, and the U.S. Virgin Islands (each significant domain with the exception of Puerto Rico).
30S 90E = None of the above. It's in the Indian Ocean (They could have meant 30S 90W. That's in the Pacific Ocean, which is on the list but hasn't been used).