The USA doesn’t recognise the ICC because they do not want their citizens to be subjected to it. There are quotes from senior officials and diplomats essentially saying that the USA agrees with the concept of the ICC but only for lawless countries where people who violate international law are unlikely to be held to account. Essentially it is a humdinger of an example of “rules for thee but not for me” creedo. The US hides behind its UCMJ (Uniform Code of Military Justice) as a panacea excusing it from subjecting itself to the rules it wants to enforce on the rest of the world. The argument is that the UCMJ is sufficient to enforce accountability and international law, and that the ICC is superfluous. It’s a tenuous argument at best and ultimately shelters the USDF from international accountability for their actions.
One of the big reasons is that GOP control congress atm. The jackasses who flouted their responsibilities and legal obligations to answer to congress (under this administration and Biden’s) have been republicans. They knew that Dems didn’t have the stomach and/or the numbers to prosecute them or hold them accountable for evading their responsibilities - so the repubs called to give evidence or testify in front of congress just did what they wanted with impunity.
Fauci is a persona non-grata with this administration and its party as a whole. Fauci knows he’ll be subjected to any and all prosecutorial avenues the GOP can utilise. I believe the thinking is this is the surest way to protect himself. His legal way to say nothing without lying, maintain his own ethics and morals, abide by the law and his obligations under it, and ensure he doesn’t give them one iota of ammo to use against him in future actions.
TL;DR: Fauci has integrity and believes in the rule of law.