You seem to conviniently left out one of the most important factors. At the time of United States founding, the resource per capita in US was much higher than any major European powers. By the way, United States was not poor, but rather high by 18th century standard. Here, I am quote Wikipedia "In colonial America, the standard of living was high by 18th century standards. Americans could choose their diet from a diverse range of plants and animals from Europe and the Western Hemisphere, and this, combined with favorable weather conditions, ensured that Americans never had to deal with harvest failures. There was little exposure to epidemic diseases, and low wealth inequality, ensuring that even the poor were well-fed."