It’s from a little-known Dos Passos nonfiction work called The Ground We Stand On.

We have taken the accomplishments in state building of the seventeenth century colonists…for granted, as we took the rich forest loam and the coal and the iron and the oil and the buffalo. We have wasted and exploited our political heritage with the same childish lack of foresight that has wrecked our forests and eroded our farmlands and ruined the grazing on the Great Plains.