While the coup itself was a the work of the Chilean military, the Church report clearly states that the CIA poured millions of dollars into the country, funding anti-left media outlets and political organizations in the decade leading up to the coup. From bankrolling the major santiago daily to providing nearly half of the campaign budget for the christan-democrat representative in the 1964 election. They certainly wanted a coup to happen after 1970, and would have been actively involved in planning it had the Chilean military not given them the cold shoulder.

US policy was to fund and spread interventionist propaganda meant to dehumanize supporters of the left and destabilize the country. The US certainly bears a share of the blame for its persistent efforts to help create a polarized political situation that shattered the country's political consensus and unleashed the military's violence upon it's own citizens.

Source: https://www.archives.gov/files/declassification/iscap/pdf/2010-009-doc17.pdf