The street reflects the abstract characteristics of the political body: it is as such a space where politics and morals are grounded. Comparing the curving lines of European streets, result of centuries of history, to the American gridiron, symbol of the historical consciousness of a new beginning, leads us to explore the elaboration of an ideology, relying on geometry, in order to better oppose the New World and Old Europe. After the beginning of the French and American Revolutions, the design of the streets of Paris and Washington, D.C. illustrates the difficulty to conceive the urban space of the tabula rasa, and national regeneration when the latter is confronted with the assertion of the necessary split between the Old and the New World. We carry out our study within the broader framework of the ideological process of the naturalization of politics.