There are simple rolls which wrap, fish and rice in seaweed. Sometimes wa few, sparse other ingredients like shallots or cucumbers make there way into the roll.
Then, Sushi gets taken to America, and what I can only assume was a creative solution to the problem of limited access to fresh fish, sushi was transformed into the decadent "maki" rolls that dominate sushi menus in the US. Cheese, fruits, vegetables, fish, meats. US maki rolls that have nearly a dozen ingredients are not uncommon.
Both styles of sushi are amazing, though very different. More like cousins than the same type of cuisine.
Reminds me of how cocktails were invented during prohibition to mask the bad taste of moonshine. Japanese shushi is to American maki what wine is to martinis.
I think when cuisines get transported to foreign counties, they get changed to adapt to their new environment.