You are right TT. Sasquatch - being the "other tribe" as described by many NA tribes - without question followed the major rivers flowing east and southeast off the great divide just as the NAs did. All one has to do to see that statement is true is pull up a map of the country's river system, then a plot of the locations of the old major NA communities and camps. Now plot the Sasquatch sighting reports on that map. You will notice that most of the sighting reports of Sasquatch come from the same areas that was once home to vast populations of NAs. (Sasquatch was not forced to move to less habitable less sustaining areas and reservations.)
When NAs and Sasquatch reached the south and southeastern coasts and could go no further, the populations of both increased to the point that many followed the rivers back upstream and began settling along the larger creeks and river forks. The NA's of course were forced to stop doing that hundreds of years ago; but Sasquatch still do that. That is why they are often seen passing through large cities which have major rivers passing though or beside them.
As a result, most of the south/southeastern states have areas in which the population density of Sasquatch per land area exceeds any other such area in the PNW. One state that is a good example of that is Texas.