Whether or not the US government recognizes Maduro as head of state of Venezuela should be beside the point. "Normal" governments would submit an extradition request. If the request is granted, fine. If not, they're SOL. Being the biggest dog in the junk yard does not grant it any more rights, privileges or authority. We're seeing a turning back of the clock to a time when international law wasn't a thing.
In reality, it may be beside the point. I'd have to read the court filings, but it appears to me that the U.S.
did recognize Hernandez as president of the Honduras, but it apparently didn't help his case.
>>>“
As President of Honduras, Juan Orlando Hernández abused his power to support one of the largest and most violent drug trafficking conspiracies in the world, and the people of Honduras and the United States bore the consequences,” said Attorney General Merrick B. Garland. “Thanks to the diligent work of the Justice Department’s agents and prosecutors, Hernández will now spend more than four decades in prison. The Justice Department will hold accountable all those who engage in violent drug trafficking, regardless of how powerful they are or what position they hold.”<<< (emphasis added)
I'm not sure that not recognizing Maduro as head of state will ultimately make much difference. In legal terms, he's probably praebibo (Latin for toast) either way when it comes to an immunity defense (yes, that was another lame attempt at humor).
Of course, given that Trump pardoned Hernández, the issue is now moot in that case.
FWIW, as I see it, a claim of diplomatic immunity as a defense does not depend on the legality of the actions taken to bring the defendant into court. In other words, my understanding is that Maduro either has immunity or he doesn't, regardless of the circumstances of his capture. In theory Trump could face legal consequences for violating the law, but I don't see how that determination would create or destroy diplomatic immunity for Maduro.
The above is certainly not an in depth evaluation of the issues.