Of course supporting people who are fighting for freedom for democracy( as opposed to those fighting for freedom to oppress others) is something the U.S. should principally do.
But a well thought out plan for going in, winning the conflict, managing that particular nation's affairs till that particular nation can manage them itself while successfully maintaining freedom and democracy for all and finally for getting all of the troops out has to exist before anything is done.
The Bush mistake was seeing the winning of a war as simply winning military battles. If you don't have a clear plan for solving the social problems that follow along with a clear departure plan for your own troops you should stay at home.
This was something that Clinton managed much much better than his successor.
Never forget, these are people (the soldiers) you're sending in there. With certainty, some of them will be killed there. Many will be killed if the operation is poorly planned. Every soldier knows that death is a possibility in case of war but no soldier wants to fight, possibly die in a stupid and poorly planned fiasco.