I'll give it a shot (being a very old motorsports fan of several genre's:
I'll ask an innocent questions: how much is "the environment" changing attitudes about fast cars, drag racing and motor "sports" in general?
Motorsports in general is being negatively affected by the switch out of petroleum vehicles but it is still a major pastime for many (probably aging out though as newer "car guys" are not being minted like the old days).
Drag racing used to be the ultimate motorsport. "Run what you brung" was the order of the day and there were classes for everyone. Now it is almost a pure exhibition sport and the costs/technology are so far out of sight it is no longer a participation sport for the "little guy". The recent change from 1/4 mile tracks to 1/8 mile just killed it. Instead of making the tracks safer (speed and runoff areas) they shortened the tracks which kept car costs as high as before but lost a lot of interest.
Sports cars and F1 are so foreign to most American fans (who also apparently don't like road courses either) they are almost an afterthought. The whining and bitching by the F1 teams and drivers has ruined that series not to mention the constant rules changes and politics. The only people caring about sports cars are the teams themselves or the manufacturers. Trans-Am racing used to be great but the decline of the American muscle car killed those.
Boat and airplane racing have always been niche events. Likewise off-shore hydros. Only good for "wipe out" video makers.
Motocross in the USA seems to be as popular as always but other forms of bike racing have just about died (hill climb, flat track, TT scrambles etc.). And once again it is a young man's sport almost exclusively. Stadium racing still seems to fill the seats but fans age out very quickly.
Kart racing is still going strong and is an ideal dad/kid club sport. No professional link though.
Desert racing (Mint 400, Dakar etc.) are interesting to watch on the telly but are not near the general population. Most local dirt tracks, and the deserts, have been restricted for many years now which leaves places like Glamis the only suitable area for the average racer to have fun in the sand.
To clarify, the world is transitioning away from fossil fuels and kids are learning about the environment in school and taught "petroleum = bad" and "wind and solar = good".
Most young people today can't drive a stick or anything without a full nav system and a trunk full of loud speakers. And the cost of fuel does a lot to ruin the "car guy" mentality as well. Emissions equipment and fuel efficiency requirements have made most cars too expensive and difficult to work on. The world is now wonking on lifted trucks.
Anyway, I've always thought that a radio broadcast of a motor race to be about as fun as play-by-play of a domino match (which I have heard on WTIL-1300!
Try listening to a Brit or Aussie call a F1 or V8 sedan race. It's worse than being inside the car. Where are you now Jackie Stewart or David Hobbs?