Partnering and Leveraging Assistance to Stop Trash for International Cleaner Seas Act or the PLASTICS Act This bill authorizes the Department of State and the U.S. Agency for International Development (USAID) to prioritize and advance global efforts to prevent and reduce marine debris and plastic waste. The State Department and the USAID are authorized to work with private-sector and nongovernmental entities to complement such efforts. The bill also authorizes the U.S. International Development Finance Corporation to establish an initiative to pursue investment opportunities to address plastic waste pollution and support improved waste management systems in developing countries.