After I finished all of my U.S. state flag redesigns, I decided to take a stab at designing new flags for the territories! Here’s the symbolism:

American Samoa

• The triangular pattern is taken from the existing flag, just flipped to be more prominent when waving.
• The red, white, and blue symbolize American Samoa’s link to the United States.
• The color arrangement—a field of red with a blue shape on the left and white symbols within the blue—is similar to that of the Samoan flag.
• The war club and fly-whisk are symbols of Samoan leaders.

Guam

• The blue field stands for the vast ocean surrounding Guam.
• The red symbolizes the violent history of the island.
• The two shapes are meant to resemble a slingstone and a sinahi necklace, both Chamorro symbols.
• Yellow is used to represent the hope of a prosperous future and so that the center of the flag resembles islands in the sea.

Northern Mariana Islands

• The blue once again represents the ocean.
• The white slopes on the sides of the flag evoke the Mariana Trench, which lies near the Mariana Islands.
• The latte stone in the center of the flag is a Chamorro symbol.
• There are 14 stars for the 14 islands in the territory. The red and pink resemble that of the original flag’s wreath, a symbol of the Carolinians.

Puerto Rico

• The white stripes are now yellow to better symbolize Puerto Rico’s Spanish history.
• The rest of the symbolism is the same.

U.S. Virgin Islands

• 'Murican colors represent 'Murica.
• The Nordic cross alludes to the islands’ former status as a Danish colony.
• There are 3 stars for the 3 main islands in the territory.

Nice work! So much better than the existing flags, both the design and the well thought symbolism. Though Puerto Rico’s flag hardly needs changing IMO, it is already great as it is.