"Europe would be entirely Islamic if the Moors succeeded"
Not necessarily true - there's an awful lot of Europe, and one victory rarely stops a campaign capable of going much further.
"Then, there would be no United States because the U.S. was founded by Europeans. "
You could easily argue that there'd be no United States after a number of events - even things as obscure as French admiral Tourville intercepting William III's much smaller fleet in the Irish Sea in 1690.