(Note: this is from U.S. point of view)
I keep hearing how the glaciers "moved South" during the last ice age. But I thought glaciers moved downhill.
I can see that the glaciers formed farther and farther south as the temperature fell. But then they presumably moved downhill, following the landscape beneath them.
However: assuming the glaciers were much thicker to the North, then the (hydrostatic?) pressure beneath them would be higher than the Southern glaciers; maybe that pushed everything South.