If you go to Mexico and order a burrito, you get a tortilla with meat and maybe some onions and/or peppers inside. That's it. Rice and beans are ALWAYS served on the side. No salsa, no cheese, inside the burrito etc.
but if you go to just about any American Mexican restaurant and order a burrito you get a tortilla shell with meat, rice, beans, salsa, cilantro, cheese, three different salsas, sour cream, guacamole, leg of lamb, glass of sherry, an Allen wrench, a basketball autographed by Darrell "chocolate thunder" Dawkins etc. etc.
So who invented the "everything and the kitchen sink" style of American burritos?
Folks, if all you've got to contribute it a link to the Wikipedia page for "Mission-style" burritos, know that it's been posted - and removed - about six times already. Please take a look at the subreddit rules before you go and create more work for us!
You might also want to try asking in /r/askculinary.
Clarifying questions:
Is a "Mission-style burrito" the same thing as a prototypcially US-ian burrito that OP calls "everything and the kitchen sink"? If there is a distinction, what is it?