The genetic evidence of Argentines' ancestry seems to point out to around 15-20% Amerindian in Buenos Aires and the Pampas, and higher elsewhere. For more, see
here. Whereas in the United States, Native Americans listed as just one race make up almost 1% of the total population, and the entire Native American population (including those listed as more than one race) is between 1.5% and 2% of the total population. I think a salient difference between the two situations is that in English/British colonies like what would become the USA, there was much less interbreeding between European colonists and Amerindians than in Spanish colonies such as what would become Argentina.
I guess that rich and middle-class Argentines don't wear shorts or flipflops as often, nor do they wear shirts sporting Universidad de Buenos Aires, Univ. Nac. de Cordoba, etc. as often? I dare say they dress more like Europeans than Americans?!