Here is the list of Senators that signed the threat:
Tom Cotton, Mitch McConnell, Marsha Blackburn, Katie Britt, Ted Budd, Kevin Cramer, Ted Cruz, Bill Hagerty, Pete Ricketts, Marco Rubio, Rick Scott, and Tim Scott
US didn't sign The Rome Statute that gives ICC authority because it then would apply to them. Half of their intelligence members and past presidents could be charged there for war crimes.