You say that now, but if someone in your family dies in an accident like the WTC, you'd be pretty mad. What if the Americans, the British, and the Russians didn't get involved in WWII? Hundreds of thousands more Jewish, gypsies, and others would have died. After that, Hitler probably would have taken over Europe, then the Americas. The US got involved to save lives.
Look what happend with Rwanda. The UN left 200 peacekeeping soldiers to take care of the entire country. The US, and any other country that was involved pulled their troops out, and thousands of Tutsies were killed. It was a genocide. Now, I'm not saying that this will happen if we don't take care of the terrorists, but what if it did? What if hundreds of thousands of people died? Then would you care?