In the poem "what I learned today" by Billy Collins what this stanza means?

But this is nothing to me. No dots are connected in the vast grid of my auto didacticism. No brance pruned in the forest of ignorance, which is why I am stepping over the Flathead River of Canada and Montana's Flathead Lake and coming to rest on the Flathead Indians I am disappointed to Learn but got their name from neighboring tribes who shaped the fronts of their own heads to achieve a pointed appearance.