AFAIK - the only archaeologically proven pre-Columbian contact between Europeans and Native Americans occurred around the Viking settlements in what is today north-eastern Canada. All other claims to artifacts, inscriptions, etc. have been proven to be misleading, false, erroneous, hoaxes or (how should we put this? ) only for the extremely gullible.
Please don't take offense - but I find myself hoping that no one here honestly believes: that ancient Celts visited America, that the Bimini roads are anything but natural limestone formations created by erosion, or that the Native Americans are the lost tribes of Israel. There are so many other bizarre claims of pseudo-scientific nonsense that have been bandied about. All fly directly in the face of all cultural, historical, archaeological and geological evidence. It's nonsense supported only by garbage science and erroneous conclusions based on (often intentional) misinterpretation of the information.
The stones at "America's Stonehenge" have repeatedly been investigated and every reputable scientist that has surveyed the area has concluded that they are the remains of a late colonial or 19th century farmstead. 20th century owners of the site, looking to make it more "interesting" to visitors, and therefore more marketable, moved many of the stones to their current locations themselves.
Yes there are ancient Native American artifacts in the area, just as there are ancient Native American artifacts strewn across most of the North American continent. Dig on the banks of any river in New England and you will find artifacts. Native Americans were here for thousands - perhaps tens of thousands of years. Any disturbed ground, as where foundations were dug and built for a farmstead, could have a mix of archaeological periods scattered about the site, and an accurate archaeological record would be impossible to set. Contemporary construction techniques almost ensure that ancient artifacts are being mixed with the foundations of buildings that are going up today. I have every hope that tomorrow's archaeologists will be more astute than to think that this means that the two societies existed side by side.
http://www.bu.edu/bridge/archive/2002/02-01/archaeology.htm (includes pieces of an interview with CAS Archaeology Professor Curtis Runnels who teaches the class Archaeological Mysteries: Pseudoscience and Fallacy in the Human Past at Boston University.)
I'm going to move this post to the Americas forum as it has nothing to do with ancient history.