Mercifully, the U.S. doesn’t have the security problems of either the Israelis or the Europeans – yet. Which is to say, the time to act is now. We need a defensible perimeter, perhaps a physical wall, to protect our northern as well as southern borders. U.S. authorities should be able to identify everyone coming into this country. Terrorists may already be in our midst, but we can at least cut off the pipeline of new ones. The wall is working for the Israelis, albeit after hundreds of fatalities that might have been prevented if it had been built earlier. As for America, a wall could prevent an unfathomable number of fatalities here on our own soil.