The earliest inhabitants of North America were thought to have come across a bridge of land thousands of years ago?

Yes, this is a theory which is believed by many people in the modern world today, it is believed that people from Russia and Siberia crossed the Baring Strait when it was frozen over 20 000 - 40000 years ago and spread out across North America, and when settlers came they became know as Native Americans. However Native American's refute this theory and state they have lived on the land since the beginning of time itself.