The US foreign policy was based on the belief that the US should not get involved in other countries' business unless it directly affected the US. This was during the time of Washington.
In 1823, when Monroe became president of the US, the Monroe Doctrine was announced. This announcement had a huge change in the foreign policy of the US as it stated that the US was the only country that had the absolute right of colonizing any land in North, South or Central America.
This meant that the US opposed Europe and stopped them from taking over any land there.