The terrorists would have already won. Invest in our country. Fund education, health care, scientific research, transportation, public works, etc. to unprecedented levels. Work harder at fostering a true international community, where all nations are welcome and all points of view are taken with due consideration. The nations of the Earth are locked together like gears.
Humanity needs to learn to work as one while respecting individual differences.
Otherwise, the opportunities for disaster will only multiply out of control. Actively craft and strictly abide by nuclear non-proliferation treaties. The ultimate act of terror is only a few mistakes away. Despite the awesome threat of a nuclear device being detonated, non-proliferation seems to be anathema to the U.S. government. We teach our children that violence isn't the answer.