Final answer:
President Kennedy identified the Soviet missiles in Cuba as a threat because of their nuclear capability and the speed with which they could strike the United States, raising the stakes of the Cold War and risking immediate nuclear conflict.
Step-by-step explanation:
According to President Kennedy, the presence of Soviet missiles in Cuba posed a direct threat to the United States because they were capable of carrying nuclear warheads and could reach American cities within minutes. This proximity of Soviet nuclear capability was unprecedented and represented a significant escalation in the nuclear arms race between the two superpowers. The Cuban Missile Crisis highlighted the vulnerability of the United States and the potential for a rapid onset of nuclear war, which was a danger that U.S. policy sought to mitigate. Kennedy sought to demonstrate U.S. resolve and protect national security without triggering a military escalation that could lead to mutual destruction.
The world held its breath during this period, fearing the outbreak of nuclear war. Kennedy and his advisors were acutely aware that aggressive actions such as an invasion of Cuba might prompt the Soviet Union to respond elsewhere, potentially in Berlin, which could have led to a full-scale war. In the meantime, U.S. spy planes confirmed that missile installations were ongoing in Cuba, increasing the urgency to act.