nearly every culture boasts well-known accounts of a massive flood that has elements very similar to the biblical Flood (going back even to the time of the Babylonians).
Seems God says it was the entire earth.
God Bless
Gee, could this be because they all experienced very bad floods at some point in time? Not necessarily one that covered the Earth, however
Maybe because they all have a common ancestor (Noah) and a rich oral tradition.