I dont remember where I got that...maybe a Red Ice podcast or Nova special or something, but there are signs in the US (south west, four corners, etc) that showed fossil records and geological evidence that the whole area was flooded with sea water, and it matched up with the same time period as other great floods in other parts of the world. I can't quite remember where it was I saw it, but it was reasonable enough. I'm not suggesting the Sumerian flood was an eye witness account, as I think this flood predates that civilization, and the story of this flood has been passed down via oral tradition since long before written history, which is why many cultures have their own versions. I don't see cultures from different part of the world, during different time periods with no direct interaction, making up the same myth with slight variations. More than likely its based on a common event, whether its coming out of an ice age or a asteroid causing a massive tsunami. It was significant enough that its been passed down generation after generation.