Is there any relationship among the Native American mounds, the discoveries of North American giant skeletons, and sightings of Sasquatch or Bigfoot?

These phenomena are largely unrelated. The phenomenon of Bigfoot is in some instances a connection to the giant beings who have inhabited many parts of the world in earlier days. This is a remnant or relic of that existence. There are extraterrestrials as well who can leave footprints that are persisting in the environment and may be discovered, but these large beings have passed from the scene other than the extraterrestrial races still interfering with humanity. There are no living Sasquatch or Bigfoot beings. Many times people see images of such beings, but these are thought forms. They are like a spirit imprint observed by humans in a particular area, so they are more akin to ghosts than living animals.