While I have time for your post since they are very informative and has seriousness of thought, yet I am constrained to raise a few issues for your consideration, even if couched in my blunt syntax, for which you must forgive me!
You forget one thing - the paddy fields, the tracks and not roads, the rivers including the mighty Meghna and the wide Padma. The width is 11kms. Do read "The Lifeblood of War" by Maj Gen J Thompson (Brassey) to realise the Herculean effort required and which is no comparison to Iraq. I dislike the words, but then what could be better to explain than the words - apples and oranges!
Too bad, what? All countries would say the same for any fiasco. The British are then equally justified for quitting Iraq, even though they did a good job inspite of lack of funds and equipment.Becuase the US Congress cut funding and supplies and would not send the US Military back in, the ARVN didn't have the tools or weapons to fight.
One can conjecture.If the US had unleashed its might earlier North Vietnam would have folded the same way they did during the Christmas bombings. But as a nation we didn't. LBJ thought you could fight a war on the cheap but limited wars only work when both sides are playing for limited objectives and North Vietnam was playing for keeps.
Iraq should be an example what the Communists could have done!
The real masters of insurgency are the Communists.