When the US was formed, capitalism flourished briefly.
The economy of the colonies flourished because of the support of merchant princes. These new breed of economic barons became wealthy as a result of the Industrial Revolution. The revolution, in turn, was financed by the taxes generated from the Jamaican sugar industry. Post independence, the American socioeconomic model is extremely socialist - especially for entrepreneurs.
Capitalism, as we know it today, only emerged in the mid-19th century when more businesses began to emerge independent of the arms of the aristocracy and its proxies. However, its incredible success was achieved on the back of low-to-zero labor cost of slave laborers and an enormous amount of natural resources and land.
The issue is a complex one.