This would be a national disaster, a self-inflicted humiliation of the highest order for the United States. Basically, America throws in the towel, rewards those killing American troops and sells its only ally, Israel down the river. The American Moment in history would be gone forever and every one would know it. The Baker Study Group proposal amounts not to "peace in our time" but to a recipe to the next war.
"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." -Manuel II Paleologus
This would be a national disaster, We would never be trusted again. Hell, even I wouldn't trust us. They would see it as, 'if the US gave up Israel, what chance would we have'?
If we do this, we are truly lost as a country.