The cartoon below pretty much summarizes the current world scenario.
The Americans trained and armed the Taliban in Afghanistan through the Pakistanis to counter the Soviets. When the Soviets were gone the Taliban took over and when 9/11 happened, the Americans shattered the country in search of Osama. But now Osama had friends in the Oil rich Saudi and other Islamic nations, he continues to evade the Americans. Even if Osama dies he will only become a Martyr. Osama and his group of capricious freaks who call themselves Al-Quaeda have already attained a cult status that wouldn't die down even if Bush's army hunts down every single one of them.
With an unfinished war in Afghanistan, Bush set his sights on Iraq. Again it was the west that armed Saddam to counter Iran. There was no doubt for the Americans that WMDs existed because it was they who trained and helped Iraq build them in the first place. Either the WMDs are well hidden or have already found their way to some terrorist organization to be used against the west in the near future. Like 9/11 and 7/7 those incidents would also become symbols... Memories... Reasons for further witch hunts.
The arbitrary Slaughter of innocent civilians like on 9/11 and 7/7 are not crimes against the US or UK but against the whole humanity. Nowadays terrorism is seldom based on justifiable causes, they are rebels without a cause, if not the US or Europe there's always Israel or India! For that reason Terrorism will not and cannot succeed in a civilized world.
Religion and not politics is the motivator of present day terrorism for that reason the 'War on Terror' will never succeed either. Bush's War is so dishonest and unmindful of the root cause. Dishonest because America discriminates between terrorist and terrorist. While transfer of Nuclear technology by Pakistan was acceptable, potential acquisition by Iraq was not. Unless we remove the conditions that feed terrorism, Terrorism will continue as long as humanity exists...