I would say the Jim Crow laws
Monroe doctrine was the thing that blocked other nations from coming into americas. It was enforced by the british military who were the strongest at time.
Many nations accepted this out of fear of their military.
Established the power of judicial review for the US supreme court and lower federal courts, judges determine wether or not a law is unconstitutional or not, which led to US involvement in the french british war in 1803
C because muslim women were treated as the lowest class in their society
