Depends which sport, dressage seems to be dominated by the Germans and the Dutch, the British are pretty consistant with Eventing, Polo = Argentina, Showjumping is mainly the USA, Germany and Switzerland, also maybe Sweden.
Personally I'd say Germany, with Britain second.
Equestrian
I believe it is anything to do with horses, for example equestrian sports are sports such as showjumping and dressage.
Equestrian is a sport that involves horseback riding. To the best of my knowledge there are no sports that begin with the letter x.
There are five sports in a pentathlon. The modern-day pentathlon has events in shooting, swimming, fencing, equestrian and cross country running.
Hunter Jumper, Jumpers (like timing), eventers= cross country, and Show Jumping
equestrian
The United States is normally thought of as the best country at sports.
Equestrian Sports (sports pertaining to horses).
equestrian
Equestrian events
The Federation Equestrian International is the governing body of equestrian sports. The FEI headquarters are based out of Lausanne, Switzerland.
dressage belong to equestrian sports(horse sports)