Is this type of air racing using modified aircraft unique to the USA?
I doubt it would be allowed in the UK due to the sort of modifications being made to the aircraft being outside the regulations.
I have to admit when I visited Reno Air Races in 98 seeing the aircraft in the pits was far more interesting than watching them fly as they were far too far away to really appreciate.
Still an amazing venue that's left me with lots of positive memories.