I don't like abbreviations but I think prefixes are an exception. Also, I found I had a few relatives that were actually named Doctor when they were not real doctors, (just had that name).
Jr. and Sr. are suffixes. And the guideline is to use only that which was their suffix at birth. Therefore, it stands to reason that Sr. should preferably never be used in the data field but rather only in the biography.
Also, I like USA better than United States of America, UK as well (worldwide recognition).