Yes a burrito is a sandwich.
Basically a sandwich is any food that is placed between something such as bread, Tortilla etc.
So yes a burrito would be a sandwich.
Also the NY State Department of Taxation and Finance department considers burritos to be a sandwich when they are taxing people for it.
Not only are burritos considered to be a sandwich in NY state but also hot dogs are also considered to be sandwiches especially when the hot dog is placed in a hot dog bun.
If the food is in between something such as bread, or other food such as the Tortilla then it's considered to be a sandwich.
Although most people think that only a sandwich is something with just bread such as ham sandwich etc they are not only the sandwiches that exist.