The defense systems being sent there are not only highly advanced, but are also extremely expensive to the taxpayer, as well as the training to operate them is compartmentalized under high levels of secrecy even against allies such as Israel.
It would be irresponsible for the military to send it over there without the proper personnel with the right clearances and training to operate it.
If you don't believe me, try joining the military and attempt to become a Patriot Missile Battery operator and let us know how it goes with the many times your background check fails.
The US has decided it wants those missiles intercepted,
Assuming the weapons system and personnel in question are used exclusively for missile intercept, then this deployment can be seen as an attempt to reduce further escalation of the ongoing conflict.
The system is incredibly expensive and purpose built.
There's no smoke and mirrors, the US is providing much, much cheaper offensive weapons. There's be no need to wire up a defensive system for that.
As context, many defensive missiles are pretty low payload, and often (but not always) use a shotgun style blast to hit the intended target. That's not well suited to ground to ground work, especially when trying to target hardened structures like concrete buildings.
EDIT Not sure why you're all downvoting. The government did literally lie to all of us about Iraqi WMD's, so I'm not sure why you'd think aren't lying about deploying troops to Israel.
I mean, we're being told that's why it is. We were also once told we had to fight Iraqis because they had nukes.
I don't think any of us really knows what's happening there.