The answer to this question is "Civil rights and feminism"
The Spanish-american war allowed the United States to connect the two coasts and establish themselves as a force on the new continent. The expansion allowed them to have allies worldwide who traded with the states and this enabled them to accumulate wealth. World War 1 was the cherry on top because it ruined the entire economy of Europe as well as European infrastructure, while US was free to produce and export since it had no economic rivalry with anyone.
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They spelled out the rights and privledges of all the citezens
The answer is: Because when the Quakers came along their ideas were revolutionary.