Doesn't the 'land bridge just mean there was a shoreline to follow with some boats, the oceanic currents still should have traveled from Japan to the west coast of Canada and all the way down to South America. Walking would have been slower and slower means more food and with ice some two miles tall it could have come right to the waters edge. Get really drunk (sleep lots) on a raft for 10 days and you would almost be there, no coming back though.
Might be news but the ancient guys were smart enough to not walk around packing rocks. When they needed one they picked it up, if they had a 'favorite handle' they would use it, toss the rock away, carry the stick to new location some many miles way and then they would find another rock that they could tie to the handle.