I didn't report it at the time.
Why not? Why didn't the three people you claimed witnessed the incident report it?
I believe a civil lawsuit would have a better chance of me winning.
I suppose "better" is true, but your chances of winning would still be virtually non-existent. What damages do you claim to have suffered as a result of this
attempted rape? Also, because the incident took place in another country, it's at least somewhat likely a U.S. court would decline to hear the case based on a doctrine called
forum non conveniens.
There were 3 witnesses to the incident
Can we safely assume you have no idea how they'd testify (i.e., you haven't spoken with any of them about this recently)?
3 witnesses . . . all . . . live in different states right now. I do not have their contact information, other than knowing their social media pages.
So...we have you in California, the potential defendant in Pennsylvania, and three witnesses in State X, State Y and State Z. For starters, where would you file your lawsuit? You could file in Pennsylvania because that's where the potential defendant lives. It's possible you might be able to file in California (e.g., if you both were California residents at the time of the trip), but you haven't given us any facts to support jurisdiction in California.
So...let's say you file in an appropriate state, and let's say that you overcome a
forum non conveniens motion. You'd then need to take depositions of the three alleged witnesses. There are proceedings for taking a deposition of a person in State X relating to a lawsuit pending in State A. However, they cost money. Your lawyer would have to travel for each deposition, and you'd have to retain an attorney in each of States X, Y and Z. You'd also have to spend money tracking down each of the witnesses to serve them with the necessary papers to compel their depositions. What if their testimony doesn't support you? Your lawyer could, of course, try to speak with them in advance of a deposition and only depose the witnesses whose testimony supports you. However, the potential defendant could depose the others.
Then you go to trial. You testify, and the defendant testifies. You can't compel your out-of-state witnesses to come to another state to testify, so the best you could do would be to play video of their depositions. Video testimony is fine in some cases, but having most of your witnesses appear by pre-recorded video is a great way to lose a jury.
And then what are your damages? You say this was only an attempted rape.
The bottom line here is that you have virtually no chance of succeeding. You probably have even less of a chance of getting a lawyer to take the case on contingency. Do you have $50,000 or so to cover attorneys' fees and costs?