Agreed. We (people) have been over here long enough that I'm sure if there was a bigfoot we would have found it by now.
On a sidenote, I'm watching monster quest on the history channel. Every episode they "almost" find the creature and then fail.
And since we're speaking of US being unoriginal - I can think of Poland, Russia, Norway, Mexico, Paris in my state alone. I'm sure there's more.