The was water. The end of the Ice Age glaciation. Enough released to carve the American badlands in a very short period of time. Just not the entire world and not all at once. Looks like a meteor impact helped too.
That's the flood there is evidence of.
And the global rise in sea level.
That's why there are human settlement remains out in the ocean. From before the end of the Ice Age.
China is cleaning house as well.