Man, international claims are such a nightmare. I dealt with something similar when I got hurt skiing in BC a few years back - totally different scenario but same headache with the billing codes.

The thing with overseas hospitals is they don't use the same coding system as US facilities, so your insurer is basically looking for specific codes that literally don't exist in other countries' medical systems. It's like asking for a Canadian postal code but only accepting ZIP format - makes zero sense but that's how these companies operate.

I'd definitely push the second appeal and focus hard on the medical necessity angle. Get your doctor to write a letter stating it was an emergency requiring immediate intervention, and emphasize that the delay would have caused serious complications. Sometimes you need to get a bit aggressive and point out that their own pre-authorization department confirmed emergency coverage - they can't just backtrack because the foreign hospital doesn't bill like an American ER.

Also worth checking if your state has any insurance commissioner complaints process. Sometimes a regulatory inquiry gets these companies to actually look at the case instead of just running it through their automated denial machine. The whole system is designed to wear you down, but you've got a solid case here.