Well, let's see
First off, they could stop the expansion of the settlements, which in itself violates the Camp David Accords, as if anyone botheres to remember them.
Second, this would eliminate support for the terrorists.
Third, the UN force would enjoy support from the surronding population in its efforts to stop the terrorists, and this is something no Israeli army will ever have.
The US could provide logistic support to this force with no problems.
ep
