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.