Whether or not its a positive difference is the manner in which they intervene. If they flood the country with food, medicine and clean drinking water it would serve as a tremendous support.
Given the levels of intervention they have historically provided with weapons, soldiers and massive bombings that too would make a huge difference. There are numerous examples of US intervention in many countries around the world. Look for yourself and determine if the countries are better or worse for the help.
By sitting on the sidelines, the United States is just continuing to let the Assad regime perform a genocide on his own people. Chemical weapons have been reported in the last several days, upping the ante. I'm not the biggest supporter of the US running around playing world police, but at some point the madness has to stop. When the government is shelling innocent people in their own cities, it's time to stop.
There are plenty of countries that could have put a stop to the genocide long ago, but nobody wants to put any boots on the ground. Due to that, the UN sits on the sideline saying "stop it guys" and nothing else really happens. We're also hesitant to arm the opposition given our recent track record with what happens when we help coups take over.
No one can make a difference in Syria except for Syrians. At this point the opposition are unorganized and have begun to fight amongst themselves, as the Syrian government continues to kill even more people. If the opposition is able to unite, then perhaps the US could make a difference by supporting them. But at this point sending equipment to an unorganized group won't make a difference, and could even make things worse.
The U.S. is currently not in a very good economic situation and also many Americans are tired of all the military action that has taken place over the past decade. Therefore, at the moment, I believe the U.S. is not in the position to make a difference in Syria. Also, the radicals in Syria would not be welcoming the military, and therefore it would simply be another expensive war.