Here's a reason why: Africans were strangers to the Americans. Because the Africans were poor, they didn't have any allies to watch out for them or to protect them.
The correct answer to this open question is the following.
You did not specify what war you are talking about. Trying to help you we are going to assume that you are talking about World War I.
In addition to fighting in the army, European colonies contributed to the war effort in that these colonies sent supplies and food to the war front in Europe.
European superpowers had colonies in Africa, India, and Asia, places where there were plenty of natural resources and raw materials that were much needed by European countries during World War I. Great Britain and France were the European countries that used most soldiers from their colonies after many white troops were killed on the battlefield.
The spread of nationalism out of Western Imperialism was a source of stress in Muslim regions of the world.
Economy: The reconstruction sought to leave the economy of the southern states, just like the economy of the northern states, however, this should be done through free labor, without the use of slaves. The plan was undoubtedly very beautiful, but it did not happen the way it was established. The southern states suffered a strong economic repression in the first years of the reconstruction and although they managed to reestablish themselves over time, the economy in these states never managed to reach what the economy of the northern states presents.
Politics: The reconstruction sought to limit the participation of southerners in politics, this did happen, but it did not have good results, since there was a great regime of southerners and moments of abuse of power and neglect of northern politicians who believed that southerners needed be punished. In addition, the laws and guidelines established in the region, stimulated the existence of racism and racial segregation, which shows that the reconstruction policy was not able to achieve its objectives.
Education: The idea of reconstruction was to build schools in the south so that people had full access to education. However, no project was carried out that showed the importance of building schools, even if this construction was carried out by northerners. The southerners rejected these schools and destroyed them again for fear that their children would be contaminated with northern ideas and this was yet another failed strategy for the reconstruction of the south.
Editorial:
Although the intention of the reconstruction was good, we can say that it was not carried out efficiently. This is because, the reconstruction failed to diminish the rejection and the feeling of disdain that southerners feel for northerners. This issue should have been an issue discussed during the establishment of reconstruction.
The lack of discussion on this topic meant that the reconstruction strategies that the government presented were rejected by the people, which made all strategies a failure.