Hmm, I was going to say "No way!" but looking around it seems like 60M buffalo back in the day [1] and at times 100M cows [2], certainly not "order of magnitude" but more cows that buffalo.
[1] https://en.wikipedia.org/wiki/American_bison#Range_and_popul...
[2] http://www.cattlenetwork.com/advice-and-tips/cowcalf-produce...