You could argue that interstates are actually a very specific part of "American culture". Certainly they had a large impact on the way of life for many Americans over the past 60 some odd years (or however many it's been). Motels, those clusters of shops around the interchanges, certain kinds of diners and truck-stops, not to mention the ubiquity of semi-trucks ("18 wheelers"), etc., are tightly tied to the emergence of the interstates and are iconic in American culture.