I agree that it is a long term program. The WTC was initally targeted under Republican administration(s) with the first physicall attack being in February of 1993.
However it is the response from the Clinton administration (who came into office with no foreign policy experience, something that the Dems then tried to use against Bush43 but that they ignored under Bush41) that led to increased terrorist attacks on US interests around the world culminating in the physical destruction of both World Trade Center towers and a considerable section of the Pentagon with another hijacked-plane-used-as-missile that did not reach its intended target.
Clearly the govt under Clinton and his administration were most culpable but the roots go back to the Carter administration.
People like Louis Freeh and even Richard Clarke have said some interesting and not very favorable things about the Clinton administration's handling of the terrorism issue. Freeh said that Clinton wasn't serious about islamic terrorism because he was chasing a right wing boogyman who didn't exist. Clarke wanted to investigate middle eastern connections to the OKC bombing but was shut down.