Why no assasinations?

What's with this taboo on assasination that the US government seems to have?  Why is it such a bad idea to send a covert unit to kill the leader of your enemies instead of carpet bombing the whole damn country, causing the deaths of hundreads of troops and civillians and costing billions of dollars? 

Assasination is a fuck good idea!  Why discount it in whole?

I can't stand this dilution of the word genocide.

"The deliberate and systematic extermination of an ethnic or national group."

What the Americans are doing is by no means systematic, nor is it deliberate. Furthermore, I'm afraid to inform you that there are no big, nasty sounding words for massive collateral damage, which is all that it simply is: the inevitable side-effect of fighting an urban war against a non-uniformed insurgency, which no-one in a democratically elected position of power anywhere wants.

When you call it genocide, you senselessly and incorrectly slander true genocides and attempted genocides, like the ones the Kurds, Bosnians, and Rwandan Tutsis were subject to.