When did the Indians first inhabit the US?

Scientists disagree about the precise date that indigenous people first came to what is now North America. It was traditionally believed that they traveled to America from northeast Asia roughly 12,000 years ago by making their way across a treacherous sheet of ice between Siberia and Alaska. This is the so-called "Bering Strait" theory, named after the stretch of water that separates Siberia from Alaska.
However, scientists from the University of Barcelona in Spain have challenged the traditional account. Skulls unearthed in Baja California in Mexico appear to have shed new light on the racial origins of the first American settlers. Although the skulls themselves are only a few hundred years old, they display certain features that set them apart from modern-day Native Americans. According to the university's findings, the more slender faces of these skulls share affinities with those of southeast Asians, who are now thought to have occupied Australia some 60,000 years ago before expanding into the Americas some 13,500 years ago.
The scientists involved in this study concluded that, instead of there being one mass migration to America, there was actually a continuous influx from Asia. Despite the findings of this research and the growing rejection of the "Bering Strait" theory by a number of Native American tribes, there is no scientific consensus on the issue. The debate and the controversy continues.
https://www.sciencedaily.com/releases/2013/04/130417092013.htm