Even "traditional" vastly over simplifies things. Every traditional dish I've learned to cook from a variety of cuisines around the world have huge variation within
the same village let alone a metro area or province.
Take borsch, for example: not only are there half a dozen or more national variations (Ukrainian, Russian, Polish, etc.) but each family has their own little trick for choosing the best meat and aromatics for the broth or ratios for and ways to caramelize the vegetables before throwing them in the pot. Most of these variations impart dramatic flavor differences when you compare them side by side. Availability of different varieties of vegetables and meat further creates a layer of regional differences
There's also an interesting phenomenon happening with the industrialization of international foods: the flavor of Thai food in the United States, for example, is dominated by the quality control of a few suppliers like Maesri and Aroy-d. Since ingredients like curry paste and coconut milk are so time consuming to make, everyone except the poorest of families fall back to the industrially produced ingredients from those suppliers, even in the home country. As the ingredients are globalized through popularity, the entire world market tends to settle on a small number of vendors, homogenizing the flavor of the dishes. There is still plenty of variation between families like the amount of fresh makrut leaves, galangal, or lemongrass and the different techniques to toast the curry paste and coconut milk and so on, but the base flavors are all very much the same.