I share your views. We can't stop a suicide bomber unless we get very lucky.
Has Al Qaeda publicly threatened Europe?
Yes, multiple times. In April 2004, Osama bin Laden released a tape offering a truce to European countries who withdrew their troops from Muslim countries within three months. The offer was quickly rejected by governments throughout Europe.
In May 2003, Ayman al-Zawhiri, bin Laden's second-in-command, released an audiotape in which he said, "O Muslims, take matters firmly against the embassies of America, England, Australia, and Norway and their interests, companies, and employees. Burn the ground under their feet, as they should not enjoy your protection, safety, or security. Expel those criminals out of your countries."
In September 2004, Zawahiri released another tape threatening countries who had contributed troops to the war in Iraq. ''We shouldn't wait for the American, English, French, Jewish, Hungarian, Polish and South Korean forces to invade Egypt, the Arabian Peninsula, Yemen and Algeria and then start the resistance after the occupier had already invaded us,'' he said. ''We should start now."