> Although the narrative of Captain America is that he enlisted in the 40's so chances of him having a turban and a beard are really really low

Interestingly, one of the first known Sikhs in the US army was Bhagat Singh Thind[1] during the first world war. He was also involved in a legal battle[2][3] for naturalization which eventually lead to the landmark decision to allow "non-whites" to naturalize as US citizens.

[1] http://en.wikipedia.org/wiki/Bhagat_Singh_Thind

[2] http://supreme.justia.com/cases/federal/us/261/204/case.html

[3] http://en.wikipedia.org/wiki/United_States_v._Bhagat_Singh_T...