The first issue of Time Warp went on sale in July 1979; the last issue hit the stands in March 1980. Unless I'm very much mistaken, Alan Moore didn't make his U.S. debut until late 1983 with Swamp Thing #20.
Folks at DC were certainly aware of 2000 AD prior to Moore, but probably mostly for the artists; back then the British writing wouldn't have been considered as important. Time Warp was probably inspired by editor Joe Orlando's past experience editing anthology books like House of Mystery and House of Secrets. Those had once been DC's equivalent of 2000 AD, after all: a training ground for new talent. I remember hoping Time Warp would be more brainy SF like Mystery In Space or Strange Adventures, but it ended up being more like the horror books.