How did this happen? Also, with this "situation" in Iraq now moving into its fifth year with no visible progress, do you think its going to end any different? :(

The Vietnam War is a classic example of how not so powerful forces can take on the big boys.
The VC had a lot to they're advantage,the geography of the country,the ability to hit and run,the fact that they didnt have to worl to a timetable and disnt have a getout clause,plus they knew that the more the US casualties ncreased the US public would eventually pull the plug on the whole operation,as being witnessed with Iraq at the present time.

If shias and sunnis were united against occupation forces it would end in the same way. But that's impossible as i see it. What's more iraqi insurgency is not supported by soviet aircrafts and air defence, and chinese "volunteers", but only by some abstract evil syrians and persians. As long as muslims kill each other, americans are able to quit without huge casualities. But the consequences are disputable here..