The results of post-war Reconstruction in the United States? and its limitations?

In the American Civil War, the northern army defeated the southern army and achieved national unification of the United States. A year later, the United States decided to develop the southern region because there were many untapped mineral resources in the southern region, which helped the national defense. and the people have developed rapidly. The United States has just unified the country. Because of the war, the national life has not improved, and the United States is facing the danger of war from European countries against the United States. After only a few years of development, the United States has become the world's number one power!