There was a debate back in the 80s/90s about how the "beringia standstill population" got into the Americas south of the ice walls. It became a bit of a pressing issue once Monte Verde was accepted as unambiguous evidence of the pre-clovis hypothesis. There were basically two main, competing theories to explain it:
1) the "ice-free corridor" / inland route, where people simply walked from Alaska to the continental US/Canada and then on to South America and
2) the pacific coastal route, where people migrated along the coast. There's a variant of this involving boats, but they're practically the same in that they post-date the first boats by a huge margin and it only changes the chronology a little bit.
The ice-free corridor was the primary hypothesis for a bit because it matched the behavior of the Siberian populations they were descended from better, but it was basically defunct by the mid 00s because the timelines on plausible ice-free corridors were too late to explain Monte Verde. Since then, PCR has been the dominant theory for pre-clovis migrations and it just took undergrad textbooks awhile to catch up. I wouldn't be surprised if even lower level classes like AP World were still teaching the inland hypothesis.
That's why studies of the PCR have focused on more southernly areas, in particular the PNW and the Channel islands. If you want lots of details and citations, I'd recommend perusing the 40th anniversary review paper: https://doi.org/10.1017/aaq.2019.80
1) the "ice-free corridor" / inland route, where people simply walked from Alaska to the continental US/Canada and then on to South America and
2) the pacific coastal route, where people migrated along the coast. There's a variant of this involving boats, but they're practically the same in that they post-date the first boats by a huge margin and it only changes the chronology a little bit.
The ice-free corridor was the primary hypothesis for a bit because it matched the behavior of the Siberian populations they were descended from better, but it was basically defunct by the mid 00s because the timelines on plausible ice-free corridors were too late to explain Monte Verde. Since then, PCR has been the dominant theory for pre-clovis migrations and it just took undergrad textbooks awhile to catch up. I wouldn't be surprised if even lower level classes like AP World were still teaching the inland hypothesis.