By forming various organizations.
The European Union, for example, unites Europe (Minus Britain these days) under one banner, thus preventing fighting.
A more direct example is the North Atlantic Treaty Organization. NATO protects the "North Atlantic" and Europe from terrorists and invading countries by using the combined military strength of multiple nations.
I think more people voted in favor of Roosevelt, because he felt the government should be spending time to help people who were in economic trouble. More people at that time blamed Hoover for the Great Depression crisis.
Black codes prevented african americans from getting certain jobs.
