The Thai government used to sponsor (not sure if they still do) Thai diaspora who want to open a restaurant in a foreign country, it was their way to market the country and attract tourists.
My main qualm with this usage -- aside from being dated -- is that all cuisines are ethnic, but singling out the hypothetical migrant's as such implies that it is particularly ethnic. So in this sense it is a bit othering.
To be clear, I don't write this to call you out for your usage or accuse you -- I'm just answering your good-faith question.
RE your point, I don't agree that it's so obvious -- cooking and running a restaurant are pretty hard regardless of where you are from!
For example Oaxacan and TexMex are ethnically Mexican, but seen as regional within their borders by the respective nations. There's deeper indigenous roots there too. Food traditions of the Jewish diaspora can't be said to be Israeli cuisine. Things that start as regionally unique become seen as ethnic over time: I dunno like rocky mountain oysters, fish and chips, buffalo wings, as they become more intertwined with the culture of those people and that culture is exported.
Ethnicity was coined to avoid the racial connotations but in the US, ethnic studies brought it right back. If one wishes to avoid the word here maybe cultural is probably the best substitute but still a bit too narrow. You'll also see Global/International/Continental/Intercontinental as well, much like in music.. but I think that misses the point too.
The term "national" doesn't simply mean "having to do with a nation state".
I promise that I do not mean to be condescending with this, but you can verify in Merriam-Webster's entry for "nationality" which is referenced by the entry for "national", or also the Wikipedia article on "national cuisine". The Merriam-Webster entries specifically give examples showing that my usage encompasses the examples you gave.
The terms "ethnicity" and "ethnic" are not problematic per se. There are a few reasons people object to usages such as "ethnic cuisine", one of which I mentioned in the comment you are replying to.
You won't find Persian national cuisine. Iran however, yes, and it's mostly ethnically Persian. You'll find food traditions of other ethnic groups in Iran as well that aren't Persian. Iranian cuisine encompasses all of that within a political border.
But it's perfectly fine to refer to "Kurdish national cuisine" or Persian national cuisine or Azeri national cuisine even in the absence of any nation state. So I'm using the term in an ethnocultural sense, not in the sense of something sanctioned by a nation state or a political entity. See also black nationalism or Kurdish nationalism -- no state is required here. You have political mobilisation around an ethnocultural designation rather than a government
Anyway. My point is that ethnic cuisine is not easily replaced by another term.
Migrants move around to follow the work. (Think more like "Nomad") Immigrants resettle in new places.
I'm reading more about it, and probably these restaurants survive based on a combination of:
- Family run, keeping labor low (labor always number 1 cost)
- Central Asian and Muslim customers (much more than just Uzbeks)
- Setting up in low-rent locations like strip malls
So a few big nights a week can sustain the family business. I guess there's a way it adds up to a profitable business.
immigrant, im- (variant of in-) ; migrant into your country
emigrant, ex- ; migrant out of your country
both are still migrants. there is no specific cause for migration required to be an migrant.
you just need to move somewhere new to live.
In terms of common usage though, it's as I said, especially in North America.
"Foreign food" or "foreign restaurant" seems to be the norm where I live, but maybe I'm uncultured. "Ethnic" wouldn't offend anyone I don't think.