this is not my opinion but what Hashem says.
The Amalekites - ancient nation who attacked us after we (Jews) received the Holy Torah. They were the Romans, Greeks, Haman. Today we don't really know who they are today but most Rabbis would say the Nazis, Russians, and other Europeans.
The Erev Rav - the Egyptians who were converted by Moses. they are the downfall of the Jews since the Golden Calf. Today they are mostly likely the Liberal Jews.