We should never have gone into either Iraq or Afghanistan. If my country had been invaded as those two countries were, I too would now be joining forces with people I may despise normally to fight the invader. Sadly our troops are being killed for an unjust war and the government should be got rid of for that reason, regardless of what they have done to the economy.
If the 'war on terror' is used to justify invading Afghanistan then what about any number of other countries that could be invaded on that pretext?
In additon to invading countries being morally wrong, Afghanistan is such an alien and complex society that 'victory', whatever that may be, is highly unlikely.
Here is an excellent article about Afghanistan by Matthew Parris.