Both off Hawaii and Cape Cod!

I think I've seen this both on the east and west coasts of North America.

Delmarva Fox Squirrels are a rare subspecies occurring on the Eastern Shore -- the peninsula east of the Chesapeake Bay. I'm pretty sure I saw this because of the blackish tint in the tail.

In Costa Rica in 2011 and in Panama in 1989

I think this is the one that I saw in Costa Rica this summer but I have to check to be sure.