If the US gov decides to project its will on your software project, an ISO standard is not going to help you at all. They will sabotage the ISO process, or force your hosting provider (GitHub) to remove your project or apply changes to it, or just kidnap your maintainers and beat them with wrenches until they comply[0].
If your threat model legitimately considers the US gov to be a hostile actor, you need far more than a piece of paper that claims what the behavior of your compiler is.
If your threat model legitimately considers the US gov to be a hostile actor, you need far more than a piece of paper that claims what the behavior of your compiler is.
[0]: https://xkcd.com/538/