My understanding was that they both (hard shell tacos, burritos) basically existed, at least regionally - or something close enough. But neither had any sort of ubiquity, certainly nothing like their role in "american mexican" food.
Real-deal hard shell tacos were waiting on industrial food production.
Deep-frying a corn tortilla so that it holds its shape was part of northern Mexican cuisine, but it's a meaningfully different dish.
Also delicious, if somewhat fiddly to make at home. Worth doing once or twice, one lowers the tortilla into the oil with something like a disposable chopstick.
