There are certainly significant downsides to training in the USA. I did my IR there.
The radio takes anything up to a few days to get used to especially if you are bad with foreign languages
They are also quite casual on the radio. But then the ATC in the rest of Europe, especially the more southern bits, can sound like they just crawled out of the swamp, compared to the perfect queens english of the UK IFR sectors.
Most rental aircraft seem not to have facilities for using headsets
That suprises me, not my experience at all. Most people wouldn't be able to fly like that.
I think America's biggest single gain is the
utility value of GA, which is directly the result of
- lots of runways
- lots of instrument approaches (no ATC needed)
- a practical private IR
and each one of these supports the other. Take out any one of them and the whole system will fall apart. If e.g. they made tower ATC mandatory for an IAP like the UK has, loads of places would lose their IAP immediately. If they brought in a Euro-style airline-pilot IR, 99% of American private pilots would chuck it right in.
Everything else, like the $100 burger runs which GA everywhere does plenty of, lives on the back of the infrastructure. There was plenty of tail-wheel stuff where I was flying but if it wasn't for the commercial/business/training activity they wouldn't have an airport.