You got some reason to show otherwise?
The war in Iraq was considered a failure because it lasted too long, and we could not eliminate American casualties from roadside bombs and sneak sniper attacks. Every "quagmire" label placed on Iraq, justly or not, can be placed on Afghanistan.
If you can come up with any plausible scenario why the war in Afghanistan will be treated any differently by those who don't think we should be at war, let me know.
As for dominoes, they are already falling in parts of Africa and elsewhere.