the significance is that in both synagogues and churches people worship the same God. (Ignoring for the moment that Jews don't accept Christ. or the Holy Spirit?) But in mosques people worship a different God. So Bush is advocating idolatry, betraying the Christian foundation of the USA.
from [link|http://www.usc.edu/dept/MSA/fundamentals/tawheed/conceptofgod.html|Who is Allah?]
Islam rejects characterizing God in any human form or depicting Him as favoring certain individuals or nations on the basis of wealth, power or race. He created the human beings as equals. They may distinguish themselves and get His favor through virtue and piety only.
The concept that God rested in the seventh day of creation, that God wrestled with one of His soldiers, that God is an envious plotter against mankind, or that God is incarnate in any human being are considered blasphemy from the Islamic point of view.
This directly conflicts with the Jewish and Christian God who created man in his own image. It directly conflicts with the Christian view of Jesus who is God as man (wholy God and wholy human).
Maybe I wasn't clear enough but what I meant was that Muslims believe that we Jews and Christians are worshipping God (their god) but we completely mis-understand who He is and what we are in relationship to Him. But it is certain that all three religions agree that there is only one true God and we are all praying to Him.
Compare this to other god based religions like Hinduism. I'm sure Muslims, as well as Jews and Christians, would say that the Hindu gods do not exist. Period.