They’re a weird American thing,

Well, no. They were invented in CaliMex cuisine, which evolved around California from Spanish and Mexican settlers, also taking some inspiration from Asian influences later.

Not only mission and california style buritoes, but also Calimex brought us taquitos as we know them, along with fish tacos.

Taco Bell probably brought them to the rest of the US and to some of the world, but they originated in Calimex.

But fusion and evolution have been the name of the game in food for centuries, even millenia. For example, look at how relatively recently tomatoes and potatoes went from the Americas to Europe and how much we consider them not to be fusion or newcomers now - but they were, not that long ago.

People disparage so many American cuisines, but especially Calimex and Texmex, and both of those are fully worthy of respect.