So much of America's power comes from its size: it is one the largest countries on Earth by population and area, and is rich in natural resources and human capital. It is also in many ways an island nation; because it faces no major threats on its borders, it is freer to project power globally.
The British Empire dissolved during the cold war, leaving the Soviet Union and the US to attend to global affairs. After the cold war ended in 1991, the Soviet Union dissolved leaving the US as the sole superpower
