He could also be less sexist by making most of the countries be represented by males

To be fair, Hetalia is practically a shounen-ai series. There is a lot of canon BL, the male characters are all very pretty boys, and one of the few female characters (the awesome Hungary) is an enthusiastic yaoi fangirl.

Normally the lack of female characters in fiction annoys me like hell, but BL series are the exception to the rule imo.