Will America's walls come crumbling down again ?

September 11th 2001 was a terrible day in America's History. This was the day when our enemy attacked our fellow United States citizens on American soil. This day showed the American people that our enemies can reach out and touch us when they really want to. Infact, this is History repeating itself because America's enemies have pulled this off before in 1941 when the Japanese came here in airplanes and bombed our country unexpectedly.
We have enemies today that are threatening to do worse than 1941 and worst than 9/11. Is this impossible ? Or will History repeat itself.