I’ve never clearly understood exactly who/what Mongols were; I know I am married to someone that is probably part Mongol, though. Some Slavs are part Mongol and that nature can definitely be discerned.
“Mongols” are of Sino-Russian ancestry, dating to several era’s before recorded history. Their native lands were in the area known today as “southern Siberia” or, more accurately, far Northern China and Siberia. Direct North Amewrican relatives are the Inuit (Eskimo).
Ghengis Khan was a mongol (or, if you prefer, JenJis Kahn). There is indication that Eastern Mongols followed the Bering Ice Bridge on the Alaskan Frontier and then populated the America’s. The impetus of the exploration was, of course, the waning of the ice-age.
Being a people of conquerors, they took the emaciated aboriginal peoples as slaves (work and ‘recreation’) and advanced as far south as Brazil. Many current Central American people have Mongolian features (AKA: slant-eyes). This is not a definitive proof, tho.
Thus, many American, Indian descendants would likely have Mongol or Inuit DNA. That is still not proof since, as a group American, Indians have chosen to NOT participate in DNA sequencing.
Gengis Khan had a habit of spreading his seed far and wide—so much so—he MUST have been a virtual sex addict—wherever he conquered. I forget the amount but the number of men with his DNA in all the lands he conquered—right up to Europe—is a shocking percentage.