You don't know what you are talking about. Believers often pray/hope that they are used as an instrument of God's will. That does not mean their will is God's will. It even expresses doubt that they are being used in such a way.
Her prayer was not for crusades or for holy warriors. It was simply a prayer that our leaders are doing God's will or that God will use them to bring about an ultimate good and it expresses a certain doubt that they are. Otherwise, why pray for it.
http://www.huffingtonpost.com/2008/01/22/obama-praying-to-be-an-i_n_82737.html
"The prayer that I tell myself every night is a fairly simple one: I ask in the name of Jesus Christ that my sins are forgiven, that my family is protected and that I am an instrument of God's will. I'm constantly trying to align myself to what I think he calls on me to do. And sometimes you hear it strongly and sometimes that voice is more muted."