Beetroot! That is one of the very last things that would cross my mind to put on a burger, and it fascinates me that you Aussies do that as a regular thing.

We have the egg here sometimes, though it's not standard. We also have definite regional variations. Here in Texas, hamburgers come standard with onion, cheese, lettuce, tomato, ketchup, pickles, meat, bread, and mustard. Often, though, they also come with jalepeno peppers and bacon.