So say if the Chinese or Moroccans had landed in America first wouldn't disease still have whiped out a majority of the native Americans.
You may be interested in these two answers from /u/rioabajo and /u/anthropology_nerd regarding disease among Native Americans. Both discuss case studies that show how epidemics were enabled by exploitative European practices, like slave trades and forced resettlements- diseases were not inherently destructive nor were natives inherently susceptible.