Why did the u. s. take action to end the taliban regime in afghanistan?

The common answer you'll get for this question is that the Taliban were a brutal islamic fundamentalists who suppressed their population and who harboured terrorists. And they did (probably the answer that you want). But the United States invasion of Afghanistan in 2003 had some very sinister sides to it- apart from the torture and violations of human rights. Prior to the Taliban's seizure of power, the pro-American government before them had granted Unocal, a US oil company based out of California, permission to pipeline oil from Azerbaijan. Interestingly Unocal donated to both George HW Bush's (1st Bush President) and his son's George W Bush's presidency campaigns and Bush Sr served on the board of the company after his presidency (basically earned lots of money from them) so if youre writing an essay on this topic, I'd recommened you add some of the stuff I said because it highlights a conflict of interest and will probably serve to balance your essay. 

Hope I helped and please rate my answer :)