Re:Cuba and the U.S. will begin to normalize relations
by jpatokal on Wednesday December 17, 2014 @06:45PM
(#8765188)
The passport you use is irrelevant: if Cuban still considers you a citizen, and decides it wants you to do military service or something, you're screwed even if you entered on a US passport.
I'd recommend formally renouncing your Cuban citizenship (and getting the documentation to certify this) if you want to be 100% sure there are no hassles.
[0] http://en.wikipedia.org/wiki/Cuban_passport