Is a wife still a wife religiously after signing civil divorce papers in America with the intention of ending the marriage legally only, and not as a religious divorce?

As long as you did not utter the divorce (talaq) or write it with the intention of effecting it, the divorce has not occurred. Your signature on the divorce case papers in a non-Islamic court has no effect, even if the court rules for divorce. Its ruling is not executable Islamically, and your wife remains under your marital protection. The Assembly of Muslim Jurists of America has clarified that if a man divorces his wife Islamically, there is no harm in documenting it before secular courts. However, if the spouses dispute over divorce, then Islamic centers act in the place of Islamic judiciary, and resorting to secular courts to legally terminate the marriage does not, by itself, result in the termination of the marriage Islamically.