The US government has been guilty of war crimes for a long time. CIA torture was investigated and war crimes proven. Brennan at the CIA then bugged the computers of Senate staff as well as others. This was discovered and investigated. Hence "The Report". 6700 pages and only 528 released. https://en.wikipedia.org/wiki/Senate_Intelligence_Committee_report_on_CIA_torture . Here's a link to the report:  https://www.washingtonpost.com/wp-srv/special/national/cia-interrogation-report/document/ . Since prior administrations were guilty of war crimes they refused to help fund or recognize the ICC. This includes the Obama drone program, CIA torture, CIA involvement in Ukraine, John Bolton pushing weapons of mass destruction in Iraq, UN troops in Serbia/Bosnia, The war in Afghanistan.