Syria needs help. Its government has no legitimacy having killed some 90,000 Syrian people and forced millions from their homes as internal refugees and into exile in nearby countries.
It would be a mistake for the United States to put its own boots on the ground, but it could help to provide a wide range of equipment (including weapons) to the insurgents. Above all, it could, together with the Arab League and others, support and encourage a transition process, carefully defined and backed by an overwhelming vote in the UN General Assembly.
It is important that the recently agreed Arms Trade Treaty was not abandoned when 100% consensus could not be obtained during the treaty conference negotiations. Instead, the text was taken to the General Assembly where there was a positive vote of 154 versus 3 negative votes (Syria, Iran and North Korea) with 23 abstentions.
In similar manner, if the UN Security Council will not act in support of the people of Syria, the GA should and can. When Russia and China will not act to serve the people, other UN member states need to take more responsibility, not less. The responsibility to protect norm is designed to place responsibility on each country to protect its own people, and when it cannot or will not, then the world community has a duty to step in. When a few Security Council states refuse to act to serve the people, then the UN General Assembly should take responsibility to protect -- using the least violence and the most international authority possible.
For the situation in Syria, the Arab League plus the UN General Assembly can give the world community the authority to act to protect the people of Syria. Then it will be up to various countries and regional groups to support the people within Syria with the supplies they need to maintain life and dignity and to assert their sovereignty.