Afghanistan should be stricken from the title. There were no pretenses on that one. The US could never just let 9/11 go, and our allies and the rest of the world agreed. Just for the invasion in itself, Bush never would have been charged with any war crimes there. No, not even in a more just international criminal system than the one we have.
Iraq is a different story. The fabrications were obvious, our allies called them out, and then we did it anyway. Iraq had no connection to 9/11 and no WMD program in active development. That was obvious to everyone at the time who wasn't a senseless warmonger. Almost as bad, it took resources away from Afghanistan, which was the fight that really mattered. Stack on top of all that the fact that we could no longer realpolitik by playing the authoritarian governments of Iran and Iraq off of each other. Iran had no direct counterbalance on its border anymore, which freed resources for them to start a nuclear weapons program. They never could have done that if they had to keep up a conventional military to make sure Saddam Hussein didn't start another war with them.
The two should be considered separately. Bush ought to be tried as a war criminal for invading Iraq, and for what happened during the long occupation in both countries. But there's no good reason for trying him for invading Afghanistan.
The Taliban-led Afghanistan was closer allies with Al Qaeda than Iraq for sure, but invading Afghanistan was also a bit of a stretch. Sure, the Taliban was harboring and supporting terrorists, but so were Saudi Arabia, Pakistan, and probably at least a half dozen other countries.
Bush is a war criminal, and while they invented the entire connection to Iraq, his administration did "exaggerate" the justifications for invading Afghanistan as well.
Look, I have no love for the Taliban, and I agree that they were supporting Al Qaeda. But there was far more evidence pointing to the Saudi royal family. Afghanistan was a convenient scape goat to distract the American people.
Saddam was a bad guy, and the world is better off without him, but he didn't attack us at all. Bush lying doesn't make Saddam or the Taliban innocent. They are all bad in their own ways.
It was clear, it was the official story, it was admitted by the Taliban and it was proven by history. There's really no reason to doubt or spread any doubt on the subject
Obama should be tried as well. He continued Bush's politics and despite knowing that newly establish Iraqi government torture its prisoners he signed a document which allowed to hand over thousands of prisoners to them. It's all well documented.