What is the largest US City without an international airport?
The largest that I can find is Baton Rouge, Louisiana (population 227,017 for the city, and 774,327 for the metro area).
I think Oklahoma City is larger, and I do not believe that they offer international in-bound or out-bound flights.
Is an airport that once served international flights but no longer does, and still has the word “international” in the name of their airport, really an international airport? (i.e. Tulsa International Airport)
That was the one I noticed as well but I didn’t know if it was correct. You run into a definition problem with these types of questions. There are some large cities in California that don’t have international airports but they are still part of the Los Angeles area. Baton Rouge is a distinct city. Providence, RI is also also fairly big and it doesn’t have an international airport either.
If to be a true international airport you have to active in-bound or out-bound service to a destination outside the US, then El Paso, would move ahead of OKC.
Jacksonville, Florida - largest city in the US by contiguous land area, and a metro population of 1.3 million - much larger than El Paso and slightly larger than Oklahoma City.
Jacksonville International Airport doesn’t actually serve any international destinations.
I’m not aware of a technical definition of “international” airport. An airport may be a port of entry with customs being able to admit travelers into the U.S., but I think you can name an airport whatever you want.
Our local field is called “Mach’s County International”, but has no customs office. I once saw a business jet registered in Canada land there, but that’s about it.
Austin’s Bergstrom “International” Airport currently offers no passenger flights outside the USA.
That will change in June, when there will be service from Austin to Cancun, Mexico.
Yeah, although I guess strictly speaking, you could define an “international” airport as one that’s a U.S. Customs Port of Entry, whether it happens to have any international flights scheduled.
According to this list, some of the larger airports I can find that aren’t currently designated a Port of Entry include:
Burbank and Long Beach, California
Colroado Springs
Baton Rouge
Flint, Grand Rapids, Kalamazoo and Tri-Cities (Sagniaw), Michigan
LaGuardia, New York City
Dayton, Ohio
Madison, Wisconsin
Not Wyoming’s Greater Green River Intergalactic Spaceport. 
However, Dayton International Airport does have regular international flights to Toronto Pearson. (It would be ironic if the Wright Brothers home town didn’t have an international airport).
There are many nonstop commercial passenger flights from LaGuardia to Canada. So again, the defintion of “international airport” needs to be defined precisely.
ETA: Also, do Burbank and Long Beach count? Or are they just part of L.A., which is served by Los Angeles International, of course? That’s anothe possible objection to LaGuardia. In this case the problem is defining “city”.
Note that U.S. airports like Dayton and La Guardia can have flights to and from Canada without having a customs and immigration facility, because the U.S. customs and immigration is handled at the Canadian airport.
Not all Canadian airports with transborder (the special term for US-Canada international flights) have on-site US Customs and Immigration services - just Montreal, Toronto, Calgary, and Vancouver IIRC.
I do have a lot of passport stamps saying I entered the US in Montreal and Vancouver, for the sake of bizarreness.
Here’s an oddity: the Coutts/Ross International Airport. It serves the towns of Coutts, Alberta and Sweetgrass, Montana; and is a true international airport: its runway is located right on the US-Canada border.
I’ve entered the U.S. at Edmonton. I’m sure there must be more such airports.
Another aspect of the ill-defined-ness of this: to what city does any particular airport belong?
Dallas/Fort Worth airport (DFW) isn’t in Dallas or Forth Worth. Does Dallas, then, have an international airport? Louis Armstrong International Airport (MSY) is in Kenner, Louisiana, and is only an hour’s drive from Baton Rouge. Does Baton Rouge, then, have an international airport? There are several large cities in the greater Los Angeles area that are further from LAX than Baton Rough is from MSY. What of them?
According to Wiki, there are U.S. pre-clearance facilities in eight Canadian cities: Calgary, Edmonton, Halifax, Montreal, Ottawa, Toronto, Vancouver, and Winnipeg. Of course, there are Canadian cities with scheduled service to the U.S. but no pre-clearance facility; these include Quebec City, London, Victoria, Saskatoon, Regina, and St. John’s.
Pre-clearance facilities also apparently exist in Aruba, the Bahamas (Freeport & Nassau), Bermuda, and Shannon, Ireland (with Dublin getting upgraded to full pre-clearance facilities later this year.)
Echoing the definition problem, Washington D.C. has Reagan National Airport which does not have Customs (but has a deal to do flights to the Bahamas where U.S. Customs has an entry port in the Bahamas for people going to the U.S.). However, the airport is not even in Washington, but in Virginia. So is Dulles, the closest international airport to D.C. Baltimore/Washington International is really a Baltimore airport that put Washington in its name for marketing purposes (some of us remember when it was Friendship Airport).
So residents of D.C. have reasonably close access to international airports, even though there are no airports in D.C. proper.