Note that the Aurochs was close to extinction at the time of the discovery of the New World.
A survey in 1564 found only 34 individuals, and the last known specimen died in 1627.
So....
To get Aurochs to the New World, you'd need to capture about half of the existing wild stock, ship them from Poland to the Americas and release them. Note that you'd have to do this before there were any permanent white settlements in what became the 13 colonies.
Have fun with that.
Basically, it's just not going to happen.