To start with, have the JWs really won more court cases than anybody else? (Whether in the USA or elsewhere). If indeed they have, then the Exclusive Bretheren would have to be close on their heels.
In earlier times, the legal system was not an avenue that was available to establish religious freedom with. Rather, during the Reformation in Europe, people had to win religious freedom by force of arms. And, typically, they attributed each military victory to their having the backing of God's Holy Spirit! (They also used that to justify their torturing to death of prisoners afterwards, too - but that is another story).
One such example of many was the Battle of Dunkeld, in Scotland in 1689. There, the Covenanters barricaded themselves into the cathederal, sang psalms, and fought off a vigorous attack by the Highland Army, which was still flush with their victory in the Pass of Killiecrankie. Of course, the successful outcome of the battle was all to do with God's holy spirit - and nothing at all to do with the fact that Highland leadership had by then collapsed!
Even in the case of the JWs, the court system acheived no success for them against Nazi Germany. In Europe, their freedom to practice their religion was likewise acheived by force of arms:
- only in the case of the Witnesses, it was somebody else who had to do their dirty work for them.
I would put their courtroom successes - where these have occurred - down to the fact that legal action was available to them. Otherwise, their claims of "success being evidence of God's spirit" are no different to those of any other religious group.
Bill.