The American Indians did not know how to do that. Yet, a few American Indians could have reached Easter Island, because of a storm, and brought the seeds of sweet potatoes with them. Also, the seeds could have been brought in the stomachs of birds. As you can see, there are several theories regarding Easter Island and the statues that reside there to this very day. Many theories have even suggested the intervention of extra terrestrials from alien planets.
Easter Island continues to be one of the world's greatest unexplained mysteries.