United States refused to become a signatory. 

However, it is false to think that World War II did not ignite nationalist feeling. In the developing world, including India, Africa, the Middle East, the Caribbean, and other places, nationalist movements developed in the aftermath of the war (and some had developed even before the war) that shook off imperialist powers, most notably England and France, in favor of home rule. 

Nationalism played a big role in the world between 1900–1945. In the early 1900s, nationalism was on the rise in Europe. Many countries began to believe that their ways of doing things were superior. They began to build up their military forces and wanted to spread their ways of life. Countries like Germany and Italy wanted to gain more land and be on equal footing with Great Britain and France. This extreme nationalism helped lead to the start of World War I.

At the same time, many countries were tired of being ruled by foreigners. Serbians wanted to be ruled by Serbians, not by the Austro-Hungarians. The same was true for the people in Poland, Czechoslovakia, and Yugoslavia.

When World War I ended, many newly independent countries were created. These countries were created based on the principle of self-determination. Poland, Czechoslovakia, and Yugoslavia were examples of countries that were formed after World War I ended. The people in these countries were ruled by people of their own nationality, bringing much national pride to these countries.

Nationalism played a role in the start of World War II. Germany wanted revenge for the harsh terms of the Treaty of Versailles that were imposed upon Germany specifically. Italy believed it didn’t get enough land from the terms of the Treaty of Versailles. Thus, while nationalism was still involved in the start of both World War I and World War II, the self-determination movement was much less of a factor. By 1945, after the defeat of Germany, Japan, and Italy in World War II, nationalism, at least for a while in most places, was a much less significant force.

1919 saw the beginning of serious nationalist movements in the developing world; these were encouraged by Wilson's goal of self-determination as part of his Fourteen Points.  However, this program was only carried out in Europe at the time, and the lines of self-determination were often drawn up rather arbitrarily not according to nationality but according to what each nation wanted.  It took the high cost in terms of money and soldiers that brought nationalism movements to the developing world in Africa and Asia. Many of the old colonial powers had lost or were in the process of losing their colonies.  This is partially due to the fact that colonies are very expensive to maintain, and the Axis powers showed Britain and France how vulnerable their assets were in Africa and Asia--it would be far simpler to let these people go run their own nations.  Of course, these independence movements took place gradually over several years, and many places such as French Indochina needed a war to get rid of their colonial overlord.  Upon independence, these former colonies often looked for a patron in either the Soviet Union or the United States.  This was the main driver of the Cold War--the developing world was not so much in favor of using the ideology of these nations as it was gaining their financial and military support.