Nice meme.

American omelettes are thicker, fluffier, have more fillings, and often have some browning on the outside of them. After those in difficulty you have French omelettes which are thinner, cheese and butter at most, and no browning. Then there's the Japanese omelette which is a whole other thing.

There's also others beyond those like the spanish omelette (which is extra thick.) and tamagoyaki (which is a rolled omelette that takes a special pan) but personally I'm not especially interested in either.