Superpower collapse is the political collapse of a superpower nation state; the term is most often used to describe the dissolution of the Soviet Union but also can be applied to the end of the United Kingdom and its overseas empire's superpower status.
Superpower collapse Wikipedia
Dramatic changes occurred in the Soviet Union during the 1980s and early 1990s, with perestroika and glasnost, the dramatic fall of the Berlin Wall in November 1989, and finally ending in the dissolution of the Soviet Union. As early as 1970, Andrei Amalrik had made predictions of Soviet collapse.
Some political scientists believe that when one superpower collapses, another must take its place so as to maintain a balance of power. During the Cold War, the U.S. fought many proxy wars against USSR-supported communist regimes, but after the Soviet dissolution found itself as the world's sole superpower, even deemed by a few to be the world's sole hyperpower. Political theoreticians of the neo-realist philosophy, (known by many as neoconservatives), self-styled as the Blue Team, increasingly view the People's Republic of China as a military threat, although there are strong economic ties between the two powers. Blue Team members favor containment and confrontation with the PRC, and strong US support of Taiwan.
The consequence of fighting two World Wars in a relatively short amount of time, along with the emergence of the United States and the Soviet Union rise to superpower status after the end of World War II, both of which were hostile to British imperialism and along with the change in ideology led to a rapid wave of decolonization all over the world in the decades after World War II. The Suez Crisis of 1956 is generally considered the beginning of the end of Britain's period as a superpower.