From about the reign of Elizabeth I through to World War 2, Britain was the world's leading military power, or strongly in the forefront at least. Likewise, due to its' naval power and reach, it was a leader in trade and commerce in Europe, due to its' superb access to the Ocean. When the Industrial Revolution began, British industry and society was among the quickest and most enthusiastic adopters of industrial technology. During the 1800's the combined factors of their seapower, industrial superiority, and strong economy combined to make Britain the world's superpower, and this was the height of their power relative to the rest of the world. There were several factors that helped the British grow so strong economically, some of them social, such as a receptive attitude towards science, the influence of Magna Carta and being the birthplace of modern civil society, and the influence of the Protestant work ethic. So, when this mercantile and civil society was transported to a continent with staggeringly vast resources, once it grew into these gifts (and started industrializing), it became glowing hot economically. The one downside America had, compared to the British Isles, is that it was a vast expanse of land, and crossing it could be rough work. What evened the odds somewhat was the invention and adoption of Locomotives, which allowed much faster transport, saving the work of many men and horses and allowing goods and materials to fly across the landscape in speed and quantities impossible for wagons, and in locations where canals were infeasible. As the 19th century went on, and America grew more prosperous, they began to excel at more and more things that Britain was formerly the lead country at previously. Due to lack of interest and relevance when it came to a republican nation considering how Eurpope's war's effected it, it stayed out of dynastic or colonial conflicts related to Europe, for the most part, except for some anomalies such as the occupation of China. Essentially, in the first 140 years or so of America's existence, its' military power was minimal to moderate, and only applied to situations where America had a strong interest. By about the turn of the 20th century, America was starting to strongly come into its' own as an economic power, swimming in food, natural resources, inter-state and international trade. The turning point in America's great power status came in World War One. After sitting out of the war for three years, unlike countries such as Canada who fought from the start, due to the strong non-interventionist sentiment in the United States, Germany finally provoked the US into going to war against it. America responded by drafting 2.8 million men, and the vast industrial capacity of the country was certainly a big help in providing all the material necessities of warfare. In the aftermath, European countries could see how powerful the US' capabilities had become; it was a sleeping superpower that had been woken up.

Anything past about 1919 isn't quite as relevant to your question, so I'll leave it so someone else.

I hope the answer was to some degree good.