One lasting effect of the Cold War is the proliferation of competing centers of power on the world stage.
The end of the Cold War meant the end of an era not just in terms of the standoff between two competing, heavily armed blocs. It also meant the end of the measure of stability the Cold War provided to much of the world. As dangerous as was the threat of nuclear war between the United States and the Soviet Union, especially during the 1962 Cuban Missile Crisis and the 1983 War Scare during which the Soviet Union misinterpreted NATO exercises as the opening phase of a major nuclear confrontation, the bipolar global structure that characterized the Cold War lent a measure of stability in world affairs.
The two main blocs, NATO and the Warsaw Pact, operated under a loose but clearly understood set of rules, and each side respected the military capabilities of the other side. The Cold War’s demise resulted in a proliferation of potential centers of power and conflict. The rise of China as a military and economic power and the continued machinations of autocratic regimes in North Korea and Iran has degraded the sense of stability that once provided a measure of security.
Another lasting effect of the Cold War is the continued mistrust and hostility that exists between Russia and the United States. The Cold War had its origins in Revolutionary Russia, with the Bolshevik regime that replaced the monarchy threatening, if only through words, the Western democracies and the United States and its allies conspiring to tilt the Russian civil war against the Bolsheviks by sending troops to northern Russia in an armed intervention that the Russians have certainly never forgotten. The World War II alliance between the United States, Great Britain, and the Soviet Union was one of convenience in the face of a common enemy, Nazi Germany. Tensions and mistrust between East and West permeated alliance relations and continued in that war’s aftermath up to the present day.
A third lasting effect of the Cold War is the large nuclear arsenals maintained by the United States and Russia, with China rapidly developing its own ability to strike North America with long-range nuclear-armed missiles. The American nuclear weapons program was initiated as a response to Nazi Germany’s military conquests and the war against Germany and Japan. There was always, however, concern about the Soviet Union similarly attaining such capabilities, concerns that proved valid when the scale of Soviet penetration of the American and British atomic weapons programs was eventually revealed. The Soviet Union’s detonation of its first nuclear weapon in 1949 was considered an important date in the escalation of tensions into full-scale Cold War mode.
There are other lasting effects from the Cold War, such as the proliferation of new nation-states in Central Asia and the status of Ukraine, but the above rank among the most important.