Broad Strokes: Given its treatment of the source material and due to the wiki-style nature of said source, there are some differences in the AU's details, though still keeping with the spirit of it as much as possible. Among the more noticeable ones include:
Canada being one of the few Nations who could call out America.
What Could Have Been: Earlier ideas for the AU would have made it much more bleak and depressing than what ultimately came out. Austria's arc alone would have involved him becoming a mentally scarred Yandere who despises his own daughter. And Hungary being little more than his subconscious...which he subsequently kills.