The answer to this question, of course, is that both wars had tremendous impacts in terms of lives lost, treasure expended, and property destroyed. In this short space, the best way to describe the effects of the First World War is to say that it led to the establishment of the Soviet Union, and that the postwar Treaty of Versailles helped create the atmsophere that led to the rise of totalitarian dictators that sparked World War II.
Aside from the almost unfathomable loss of life in World War II, its primary effect was to create a bipolar world in which the United States and the Soviet Union were the only remaining superpowers. This situation quickly developed into the Cold War as the interests of the United States and the USSR came into conflict. Another major effect of the war was the decolonization process that followed it.
Both World Wars made the world a little “smaller.” That is to say that communication pathways were formed between many nations which had little if any contact previously. Millions of ordinary citizens as soldiers travelled all around the world. As always, when this happens, cultures intermingle. Elements of culture found their ways into other cultures. When people move around the globe, they leave part of their culture as they go while also taking elements of others culture with them.
Economically, wars boost a nation’s economic status. It is easy to see why this is so. Large amounts of people must be paid to serve in the military. Also, wars create disposable goods. Weapons must be used. Once they are used, they must be replaced. A nation’s citizens must be paid to replace them only to be used and destroyed again. Support personnel must be paid as well. A nation’s government becomes a competitor In the employment pool of a nation. Unfortunately, the negative side is that once the war is over, the government pulls out of business and many are left jobless. This is post-war depression. Reparations must be paid by a nation ravaged by war. In WWI, the treaty of Versailles assigned massive reparations to Germany which led to the crippling poverty of the German people which, in turn, was the dissatisfaction that allowed Hitler to come to power.
The enormous loss of life and property in both wars generated fear of a world war 3. The huge advancements in the technology of war and killing massive amounts of people at once made citizens afraid. For example, when the US bombed Hiroshima and Nagasaki nations all over the world became afraid to the extent that they rushed to create their own atomic bombs. The major player in this arms race was the Soviet Union. As the USSR created bigger and more powerful Weapons of Mass Destruction (WMD), other nations including the USA created bigger and more powerful WMD. As the US and the USSR were the only nations which had the resources to do so, they became the major players in this arms race. An oversimplification of this process is that: the USA was afraid of the USSR; the USSR was afraid of the USA; and all other nations were afraid of both countries. This lead to the forming of alliances to both countries; the Warsaw Pact nations allied to the USSR and the United Nations allied to the USA. All of this is popularly called the Cold War. At times this war was almost unnoticeable. Sometimes, however, it became much hotter. Both nations participated in limited ways in the conflicts in Korea and Vietnam.