Cuba presented a threat to the United States because they were close to the U.S. mainland and communist
Explanation:
Establishing of diplomatic relations between Soviet Union and Cuba in May 1959 Cuba entered the area of their interest.
Cuba thus secured a strong economic partner and hoped to become a model for gaining national independence for all Latin American countries.
In the US, this was considered an attempt to bring communism to South and Central America and was completely unacceptable to them.
The alliance between Cuba and the USSR was of mutual benefit.
The Soviets were now able to make up for the tactical disadvantage due to the distance of US territories that Cuba could reach from mid-range nuclear missiles, and Cuba saw in the Soviets the most important trading partner and the protective cloak that secured Castro's rule.
