According to the Crazy Horses Songfacts, the song was written about Air Pollution - "Crazy Horses" represents automobiles - "horsepower" - that creates pollution in the skies from the exhaust.
"Crazy Horses" was banned in South Africa as "horses" it is a term for heroin, and "Crazy Horses" was seen as a reference to drug use. Source: Songfacts
There's a message
In the air
Crazy horses riding everywhere