I love this quote from Donald Cameron Watt on British appeasement, something that American politicians should reflect on whenever they try to play the historian:

In May 1945 Britain was the only power whose people could say that they entered the war by choice [edit: the French could say that in 1939-1940.], to fight for a principle, and not because their country was attacked. They entered to fight Hitler and those who supported him. ... But it is odd that the greatest reproach so often made against the Government which commanded a majority in the House of Commons and in the country is that it did not go to war against Hitler a year earlier.

Even at Munich, Chamberlain engaged Hitler, and when that failed, he went to war. Current American policy is to let situations escalate until they become direct threats to American security or interest and to wait until the problem is of sufficient magnitude as to justify the use of overwhelming force. America waits until it can "use a sledgehammer when it could have used a chisel earlier" (paraphrase of Peter Maass). It is important for US to act now in Haiti at a point when smaller forces can be deployed to deal with the situation rather than wait until it would cause a crisis of force deployment to balance interests in Afghanistan, Iraq, West Africa, and Haiti.