It is next impossible to seperatists groups for middle east, pakistan or afganistan to inflirate US terriority through sea or land, the most easiest way for them to enter US is through airport.
Border along Mexico is not secured and the white extremists groups are in real becoming more restless and they are the ones u are creating more problems now , @ shootout at Holocaust Muesuem .
Crashing Planes is the most favoured way of terrorist to cause damage(cause terror) in US.
It was complete failure of intelligence agencies .. Already international intelligence agencies informed about it to American Adm , basically Egyptian ,German ,Saudi,France agencies .
During cold war greatest danger to US came form KGB adgents(US had more problem handling KGB adgents more than soviet icbm), during that time any one with soviet decent, soviet citizen or any one who has travelled to USSR or had conection with USSR had seperate security checks.
There was an open asylum system given to Soviet nationals by the American Adm in which thousands Soviets entered America .
Currently as US is on war with terror or as i say war on muslim countries its greatest threat comes form seperatists groups in this country, US believe their greatest threat comes for muslim people.
Its because of the policies of American adm in which its supporting regimes and these regimes are suppressing people .
google USA involvement in Somalia ,Afghanistan,Iraq,yeman ,Sudan , u will get all the answers and all these involvement was long before this war on terror even begin .
It is a natural feeling that it you are in war/fight with a particular set of people you would be cautious from them and even take several steps/measure against these people to protect yourself, which may not be acceptable to others.
Yes its a natural feeeling but if u see in case of Russia its completely different even they are having problems by Seperatist Muslims .
How many terror attacks took place in US after 9/11?
there have been some terror attacks like the holocaust muesum shoot out , bomb plot by African americans and now White extremist groups are more active .
Well there were many terrorist attacks even before 9/11 . I found it a bit interesting .
1910 October 1: A bomb at the Los Angeles Times newspaper building in Los Angeles, California, United States, killed 21 workers.
1915 July 2 Frank Holt, (a.k.a. Erich Muenter) a German professor, exploded a bomb in the reception room of the U.S. Senate. The next morning, he tried to assassinate J.P. Morgan, Jr. (son of the financier whose company served as Great Britain’s principal U.S.
1920 September 16: Wall Street Bombing killed 38 people and wounded 300 others
1927: The Ku Klux Klan launched a wave of political terror in Alabama.
1933 October 10: A Boeing 247 was destroyed in midflight by a nitroglycerin bomb. All seven people aboard were killed. This incident was the first proven case of air sabotage in the history of aviation
1940 - 1956: George Metesky, the "Mad Bomber", placed over 30 bombs in New York City in public places such as Grand Central Station and The Paramount Theater, injuring ten during this period in protest against the local electric utility. He also sent many threatening letters
1954 March 1: U.S. Capitol shooting incident by Puerto Rican nationalists wounded five Congressmen
1958 October 12: Bombing of the Hebrew Benevolent Congregation Temple in Atlanta, Georgia, suspected to have been done by white separatists
1963: 16th Street Baptist Church bombing. A member of the Ku Klux Klan bombed a Church in Birmingham, Alabama, killing four girls aged 11-14.
1965: The Monumental Plot - New York Police thwarted an attempt to dynamite the Statue of Liberty, Liberty Bell, and the Washington Monument by three members of the pro-Castro Black Liberation Front and a Quebec Separatist
1995 Oklahoma City: Oklahoma City bombing kills 168 people, 19 of them children; the most deadly act of domestic terrorism in the United States to date.
2001 December 12: Jewish Defense League plot by Chairman Irv Rubin and follower Earl Krugel to blow up the King Fahd Mosque in Culver City, California, and the office of Lebanese-American Rep. Darrell Issa, foiled.
On the other hand we have two to three terrorist attack every year.
And why u think those occur ? Intelligence failure or what ?