The statute of limitations varies from one state(or country) to another for legal liability. It literally varied from a very few years, to decades.
The “statute of limitations” within the Church would also vary somewhat. As an example, a number of priests were accused of such acts from 30-4-50 years ago, but were not disciplined for a variety of reasons. In some cases, they were senile, and could not respond to any such charge. In others, other than the statement of the accuser, there simply was no evidence at all.
I personally knew a man who made such an accusation in California, collected over $40,000 from the Diocese, and then later admitted that he had never been molested at all. I reported this, but nothing was ever done about it.
For molestation to be a Federal offense, it would have to have occurred on Federal property. The victim moving to another state would have no bearing on this at all. Neither would driving to another state to commit an offense. The state laws of the state where the offense occurred would prevail in such a case.
However, if you were to take a victim from one state to another, then you might fall under various Federal offenses (but NOT for molestation itself). If you travel to another country, with the express intent to violate children, that IS a Federal offense.