Correct me if I'm wrong, but it seems that most national cuisines evolved out of a history of relatively isolated local food sources and practices. For example, sushi is considered a Japanese food item because it was not exported outside the country until it had for the most part evolved into its current standard form. Similarly, curries are considered representative of Indian cuisine because the cooking techniques and traditions associated with it had pretty much been standardized by the time Victorian England discovered it. You can say the same about many other "national" (cultural may be a better term) dishes such as tamales, stinky tofu, pho, etc. In some ways, this was possible because their development occurred during a time when geographic isolation (e.g., travel before the jet age) meant cooks could mainly work only with local ingredients. Additionally, information exchange was much more difficult and slow, and it is reasonably to imagine that food trends did not travel outside a local area as fast, if at all.
Given the easy availability of what were previously purely local ingredients and the quick dissemination information about local food trends, are we witnessing the death of new national cuisines?