A hypothesis: Areas of high ethnic diversity evolve better cuisine.
All the immigrants bring their cuisine and leave the lousy items home. With restaurants and food service often being a "buy yourself a job" type business where only a few of the staff have to be English fluent, large numbers are created and the competition keeps the prices down and the quality up. Their big opportunity for a breakout business becomes appealing to the masses and then you see everything from Pho' to shawarma.
This phenomena is invisible in all the immigrant discussions, but it is one of the better byproducts of diversity.