Why? 1) because in each case immigrants from those places wanted to expand their customer base to more than just people from the old country. So they started experimenting with things that would appeal to a wider audience of people from everywhere else until they came up with things that were hits to a broad audience. 2) America is a rich country - not just in money but in land and resources. Meats and cheeses and spices that people in the old country simply couldn't afford, Americans could afford - and wanted. We always had plenty of land to graze more cattle on and a much lower population density. When you've got the money to add more/better ingredients, surprise surprise, the dishes taste better. Then that gets re-exported to the world. America has long been an ideal laboratory.
PS. I can tell you from having been an expat multiple times, Europeans still have not discovered Tex-Mex or genuine Barbecue yet.
I went to a ‘steakhouse’ in Germany and whatever they were serving was unrecognizable to me...............
As former world traveler (business) that is very true. For example, Mexican food. Mexico has its regional fare but you don’t find the gloppy greasy mess that you find just across the border in Texas. And then have Mexican between Texas and California and they are different for the locals palate. But it’s all pretty similar. The first international Mexican food I had was in Australia. There was nothing Mexican about it except for the nacho bar that was as exotic as the nacho bar at 7-11. Cheap though and there were roadside bars that had all you can eat which was perfect for cheap eats on a road trip. Mexican restaurants were like stepping in to the set of Three Amigos.
Then Mexican food in Europe. I would stop in them out of curiosity in the cities. The funny part would be getting warnings about how spicy something was. In Warsaw, mayonnaise is spicy to them....I asked for hot sauce and the waitress brought out this ancient bottle of Tabasco someone probably smuggled across the border durning the Soviet occupation and handed it to me like it was radioactive. My girlfriend was astounded when I emptied half the bottle on the flavorless collection of “Mexican” food to give it a little kick.
Anyway. The Chinese in America use what they have for what the customers wanted. Cheap fast filling greasy glop served on rice. Comfort food.
Reminds me of a Black guy I knew in the Air Force who used to cook amazing BBQ spare ribs. He told me when he was stationed in England, he used to go to an off-base butcher shop to buy meat. One day he was in there shopping and noticed the butchers were throwing away the ribs. He asked why, and he was told that they can't sell them because nobody eats them. After that, he would go there every week and have all the spareribs he could carry for almost nothing.
True, but they are slowly getting closer. Where I am in Poland right now there's a rib place serving wood fired ribs. Not US style barbecue, but damn good. It's owned by Ukrainians, serves really good beer imported from Lvov (Lviv) on tap.
The staff are mainly Ukrainian and wear red shirts and black pants: the colors of Bandera. I would find that highly dubious, but the Poles don't seem to mind, and when I was in Ukraine they all denounced the Volhynia propaganda as Soviet lies, so I doubt it's an intentional "in your face".