During the Cold War, the United States and the Soviet Union were engaged in a military and technological competition, known as the "arms race." One aspect of this competition was the development of faster and more advanced aircraft.
The United States saw the need to build faster planes than the Russians, as part of the overall strategic and technological competition between the two countries. Faster aircraft would give the United States an advantage in reconnaissance and strategic bombing, as well as in air-to-air combat. The development of faster planes would also demonstrate the technological superiority of the United States, which was seen as a way to deter the Soviet Union from aggressive actions and to boost the morale of the American people and the international community.
In addition, faster planes would also be useful for the United States' nuclear deterrent. The US had a strategic nuclear bombing force, which relied on bombers and by having faster planes, they would have a better chance of penetrating deep in Soviet airspace, increase the chances of delivering their payload, thus making the US nuclear deterrent more credible.
In summary, the United States saw the development of faster planes as an important aspect of the Cold War competition with the Soviet Union, as they believed that having faster planes would give them an advantage in reconnaissance and strategic bombing, as well as in air-to-air combat and improve the effectiveness of their nuclear deterrent.