I think that one can make a case for American nationalism guiding some aspects of national economy in the 20th Century.  American nationalism and the belief of its intrinsic greatness helped to guide the national economy's interest abroad at the start of the 20th Century.  

As much of the world had accelerated the race for empire, American nationalism guided economic interests in the foreign sector.  Dollar diplomacy, the belief that American foreign interests are secured when national economic interests move into the international domain, became the simultaneous enactment of foreign policy and national economic pursuits in the Taft administration.  

The idea of dollar diplomacy was rooted in the notion the economic interests can help to smooth over potential disputes abroad.  One of the byproducts of this philosophy was to use American nationalism and its sincere belief in its own authenticity to generate foreign policy with other nations and sustain its own national economy.  Dollar diplomacy in the early part of the 20th Century demonstrates how American Nationalism shapes national economy because both Taft and Secretary of State Knox understood that foreign investment and expansion of boundaries was critical to sustain domestic economic interests.  

Dollar diplomacy does not work if there is not some level of American nationalism guiding it.  American economic interests cannot be broached with a country unless there is, on some level, an embrace of intrinsic American greatness.  It was in this where one can see American nationalism playing a distinct role in shaping the contours of national economy both domestically and internationally.