Which statement best describes the united states changing role in the world during the 20th century

The statements are as follows:
a) it changed from a great power into an isolationist nation, much lole japan
b) it was vastly richer, larger, and more powerful than it had been 100 years before.
c) it's losses during the war of 1812 substantially weekend it's power for the next hundred years.
d) it's strict economic control is resulted in a widespread return to mercantilism.
e) it became a military superpower in the world but like they strong economy.

African americans at the time just came out of slavery and needed money to provide for there families. so they joined for the money mainly.