Final answer:
The breakdown of the alliance between the USA and the Soviet Union after World War II was mainly due to differences in political ideologies, which led to the Cold War, characterized by arms races, proxy conflicts, and ideological competition. The conflict refrained from direct military engagement due to the threat of mutual assured destruction, but tensions continued even after the Soviet Union's dissolution with Russia seeking to reassert its influence.
Step-by-step explanation:
The breakdown of the alliance between the USA and Russia, more specifically the dissolution of friendly relations between the United States and the Soviet Union after World War II, can mostly be attributed to differences in political ideologies. The two superpowers harbored vastly different economic and political systems, each believing theirs was superior, which led to significant foreign policy clashes, an intense arms race, and competition for influence around the world. Although they were allied against common enemies during World War II, once the war ended, their common interests dissipated, and tensions resurfaced, culminating in the period known as the Cold War.
The Cold War was a multi-faceted conflict characterized by espionage, political assassinations, propaganda, and competing alliances, all undertaken with the aim of establishing technological and ideological supremacy. During this time, the Mutual assured destruction paradigm prevented direct military confrontation, but proxy wars such as those in Korea and Vietnam ensued. Furthermore, the rivalry extended into space with the Space Race, adding another dimension to their competition.
The demise of the Soviet Union led to the emergence of new nation-states and a reorientation of U.S. foreign policy towards promoting democracy and economic reforms. However, tensions continued under the leadership of President Vladimir Putin as Russia sought to reassert its influence, particularly on its western borders, leading to strained relations with the United States, especially given concerns over Russian meddling in U.S. elections.