They've (euro cryptids) have gotten nerfed over the centuries, and the especially nasty ones probably got wiped out during world War II.

Our (American) culture is strongly combative, and our last giant local war was over a century and a half ago or so. The dark things that have crawled forth from our deepest nightmares and waking dreams are far hungrier, crueller, and have had much more time to proliferate than your feeble, mischievous survivors.

Your cryptids crave petty things, like food, stealing names, or the occasional child. Ours crave the end of all things and the souls of the multitudes, to truck is into turning each hand against every other, and ultimately to drag our shattered remnants kicking and screaming into the dark places under the Earth.