A) I think obsidian is harder then you all give it credit for, if the soanish, with the mighty Toledo steel arms, and armour were nervous, if not afraid of the stuff, and Spanish steel, in paticular that from Toledo is considerd the thrid best steel in the world at the time
B)Its not is was JUST swoards and such, there were pikes, and axes, and a variety of armaments
C)I think you all expecting a big field battle btween mongols and American Indians, this would NOT have happend, one of the reasons my native american brethren were as succesful as they were is becasue of ambush tactics,
D)I dont think the mongols would have many natives on there side considerding all the diseeases that 30,000 mongols, and friends would be carrying
E)why dose every one assume that tribes would be indipendent? sure, the mesoamericans were, but NOT the north american tribes- they banded together, and often had a very good amount od succes considering the were "stone age bow armed primitives" not just against the early europeans, with there primitive guns, but righjt up into the 1900s' with the same wepons, though with the addition of the horse.
which brings me to-
F) in an army of 30,000, in a new land, with unknow dangers, the thought that horses would all be kept accounted for is silly- it has happend all the time in armeis all over the world, animals escape, which could bring the horse into contact with the mighty Native American Braves