Potentially offensive if the viewer chooses not to take it as it is- a light, prodding parody which uses history and historical settings as a buffer. The characters are - including the girls- generally attractive individuals, all based on some societal norms and the stereotypical quirks each homeland may possess. The anime remains faithful to the strips and the strips can be oh so delightfully campy.
If you're looking for entertainment with a colorful cast, surprisingly subverted (or not so subverted) educational value and a splash of 'shounen-ai' (depending on how you want to look at it), then Hetalia may certainly be something to look into.