Spot the odd flag out

I visited Hawaii's most popular attraction, Pearl Harbour, to see the sites of America's 2 most famous battleships. Arizona, a war grave which sustained the heaviest casualties during the attack and was left as a tomb for the 1000+ who died inside. And Missouri, the last working battleship, on which the Japanese surrendured in 1945. It was only decommissioned in the 1990s.

I also saw this collection of flags on a US WW2 submarine, showing the ships it sank. Suggests that US-French animosity predates the whole 'Freedom Fries' nonsense! For extra points, can anyone tell me why the US was sinking French ships?

Now in San Francisco with my latest couchsurf host.