Why Afghanistan can't be conquered ?

14 American Die in Afghanistan
2 Helicopters crash after a firefight  in Afghanistan. This appears to be the deadliest crash in 4 years . While the Pentagon is reporting that it was an accident , many speculate and believe that someone is covering something  up . This year had been the deadliest year for the coalition forces in Afghanistan . The Taliban are on the offencive , while the Us and other nations are in the retreat mode.  Rumors are going around that the country is ready to collapse in to the Taliban hands .  Taliban are getting closer and closer to the capital Kabul .  Why this is not being reported my media is unclear right now. Even President Obama is now considering series talks with the Taliban. 
Why do we feel that we can do a batter job that the Russians did 20 years ago?
 Russians spent billions and did everything possible to defied the Mujaheddin fighters , but ended up saying that ' even if we kill every Afghan in the country we still wont be able to conquer ' . 
One tip I can offer the US Defence Department , Is that the way we are fighting in Afghanistan is not working , and never will , even if we bring a million more troops to this region. 
The Roman Empire Could never conquer the Arabia , why? Well its just the sort of people the Arabs are. So what did they do ? They first conquered the country , than they left and let them  rule themselves . Of Course the Roman received tribute from them , and needed to go back in to subdue the nation every once in a while . But the Romans let them rule then selves.
What the US needs to do is let Afghanistan  govern its self , Whether it be the Taliban or the Karzai government , but we need to use our primary weapon 'air supremacy ' to come in from time to time and put them in check  if our interests there are not obeyed and met. 
Many Russian Generals also agree with me .