Legal Question in Criminal Law in California

If not in the US, I'm not aware how a US crime could have been committed.

Despite that, if you are aware of, or had been notified of, charges filed against you, then an analysis of specific tolling and statute of limitations issues could be done. Other than that, guesses and speculation are of no value.

There are many ways to violate U.S. criminal laws from outside the U.S. For example, someone who defrauds an American (by mail, phone, email, etc.) can be prosecuted for it even if he was in another country at the time.

But you haven't provided enough information to tell you what the applicable limitations period(s) might be. One reason is that different crimes have different limits. Another is that the same crimes can have different limits in different jurisdictions. Further, it's often not obvious when the time begins to run.

This website isn't set up to give specific legal advice; that's true even when the user provides a lot more detail. You should consult with an attorney in the jurisdiction where you have been/might be charged. He/she will be able to offer more concrete guidance once you've provided more info.

Good luck.