Complex sentence: Due to the influence of this development to the U.S. economy, the Reagan Administration began the "anti-drugs certification process" in the late 20th century, which allowed the U.S. to intervene in activities related to illegal drug transport in Latin America.
Split into simpler sentences: Due to the influence of this development to the U.S. economy, the Reagan Administration began "certifying" countries for their attempts at controlling drug trafficking. This allowed the U.S. to intervene in activities related to illegal drug transport in Latin America.