Your analysis of the processes is great, but drumlins have nothing to do with glaciers. You can find exactly the same patterns in Australia, the Sahara and the Gobi deserts. In fact you can find them all over the Earth. They are caused by fast flowing water. Follow the vectors of the drumlin fields in North America and you will find that they travel in a general south west direction from Baffin Island to Baja. There are also several interesting mixing regions in northern Canada where flows have collided.
