Were there many pretend cowboys from New Jersey?
Good question. I guess to answer this someone would need to know what a real cowboy is. By definition it is a man, typically one on horseback, who herds and tends cattle, especially in the western US and as represented in westerns and novels.
It can also mean a person who is reckless or careless, especially when driving an automobile.
There is a place called Wild West City which is a Wild West theme park based on 1880s Dodge City, Kansas, located in Stanhope, New Jersey. There are probably people working there who act like the western, horse riding type cowboys.
Bruce Willis was raised in New Jersey. In 1988 he played the role of Tom Mix, a cowboy in the Western, Sunset.