To what extent was US foreign policy the cause of the Cuban Missile Crisis?

To a large extent these economic policies caused the crisis. However other factors played a part. These include the need to establish nuclear parity (equality), and the pressure under which leader found himself.
The US foreign policy of protecting its economic assets caused the Cuban Missile crisis because it pushed Fidel Castro into the Soviet Camp. The US government objected to nationalisation of US assets in Cuba, including sugar plantations and an oil refinery, They placed an embargo on the purchase of Cuban sugar. Castro felt compelled to find a new market for the sugar and drew closer to the USSR when Khrushchev offered to buy the sugar harvest. Castro began to describe himself as a communist. This brought him into conflict with the second aspect of US foreign policy-preventing the spread of communism. The Cuban Missile Crisis developed from this because it led to an attempt by the USSR to protect its new ally with nuclear missiles. The US had tried to topple Castro in its Bay of Pigs invasion of April 1961 and Operation Mongoose. They looked likely to try again unless the island could be defended with nuclear missiles, which would deter the US government. To a large extent therefore the missile crisis was caused by US foreign policy.
However, whilst the above factor was crucial, it was not the only factor. The Soviet need to create parity in the nuclear arms race was also important.
USSR had fewer ICBMs. Khrushchev wanted to place MRBMs in Cuba to make up the missile gap. Khrushchev saw this as a defensive strategy-but Kennedy interpreted it as an unwarranted escalation of the nuclear arms race to be firmly opposed. However, some historians would argue that the attempt to create nuclear parity was really driven by the aggressive US foreign policy. The US had placed MRBMs in the UK, West Germany, Italy and Turkey as part of its policy of containing communism. They pointed hostile weapons at the USSR to ensure the Soviets did not make a move on Berlin or West Germany. It could be argued that Khrushchev’s  MRBMS in Cuba were really a response to this policy. This would imply that US foreign policy was the most important factor in causing the Cuban Missile Crisis.
Whilst US foreign policy was the most important in causing the Cuban missile crisis we must also consider the impact on each of the protagonists of the pressure they were under.
Kennedy: Facing midterm congressional elections. Looked weak at the Vienna Summit in July 1962. Failed to give a firm response to the erection of the Berlin Wall. Had looked foolish for authorising the Bay of Pigs invasion in April 1961. So he was unlikely to back down over the Cuban missiles
Khrushchev: Faced domestic opposition to his agricultural reforms. He was also under pressure to reset the USSR’s leadership of world communism, a role that Chairman Mao Zedong of China would happily take over. 
Of the two, the pressure that Kennedy faced was the greater because the US was a democracy and his need to win back public opinion was greater than Khrushchev who led a single-party dictatorship.
In conclusion it can be seen that US foreign policy was the most important cause of the cuban missile crisis. The attempts to contain the spread of communism in Europe and the Americas. The attempts to contain the spread of communism in Europe and the Americas pushed khrushchev to seek to defend his newfound ally, Fidel Castro. He chose to do so by placing missiles in Cuba. It is true that khrushchev may also have been motivated by a desire to re-establish nuclear parity, but that desire was heightened by the aggressive nuclear weapons which the US had placed in Turkey, Italy, Uk and West Germany, as part of its foreign policy. Finally, the personal pressure which each of the leaders felt under was also a factor, but much less important than US foreign policy. This is because most of the pressure on Kennedy arose from that foreign policy. The attempts to contain communism lay behind the tension he experienced in both the Bay of Pigs and the Berlin Wall. Therefore we can see that to a very large extent the Cuban missile crisis was caused by US foreign policy.