You can, on common example is Sex crimes, a US Citizen can (and have been) charged with violations of various sex crime laws for actives that occurred outside the US in courts INSIDE the US, even if the activity was not a crime in the nation the activity took place in. aka "Sex Tourism" [1]
You can also be tried for Foreign crimes such as bribery in the US if you were bribing a Foreign official this applies to business as well as government.
[1] https://www.ice.gov/news/releases/ice-homeland-security-inve...
Yes.[1][2]
As far as the US is concerned, the Constitution is the supreme authority to which Americans can and will answer to and is protected by.
[1]: https://en.wikipedia.org/wiki/American_Service-Members%27_Pr...
[2]: https://en.wikipedia.org/wiki/International_Criminal_Court#U...
[2]: "[Bolton] added that the U.S. would do everything 'to protect our citizens' should the ICC attempt to prosecute U.S. servicemen ..."
So, I do get what you're saying. If it were federal employees directly participating they can be prosecuted in the US.But if this is done through a web of contractors it will be hard to prosecute.