I'm not posting from inside the US, which is why I expect I was asked. In my search, it's clearly "Gulf of Mexico." When I do a search specifically for "Gulf of America", I get the exact same image, which includes the name "Gulf of Mexico" right on the map, and the description says "Gulf of Mexico."
Here's what Google said on the subject-
Gulf of America name change in the U.S. — what you’ll see in Maps