Sorry for the double post but I couldn't edit, waited too long. Now that I've found coffee I can articulate a bit
Your excerpt is true, the US signed and ratified all four of the original protocols.
Here is a link which provides info on that.
Geneva Conventions 1949 - United States of America reservation text
In reference to topic at hand, whether or not guantanomo prisoners should be subject to it, or prisoners from this war...whichever..
The parts you referred to in 1977 are commonly known as the additional protocols - the US did not ratify these.
They are:
I. Protection of victims in armed conflicts to situations where people are fighting in the exercise of their right of self determination against colonial domination, foreign occupation, or racist regimes.
II. Protection of victims of internal conflicts in which armed opposition controls enough territory to enable it to carry out sustained military operations.
Source for ^^:
Geneva Conventions - MSN Encarta
So, the cases of Gunatanamo, Iraq, Vietnam, Korea, and pretty much every single colonial war are not applicable to the Geneva protocols.
By not ratifying these protocols, the US is essentially open to disregard protection of victims in armed conflicts surrounding colonial domination, foreign occupation or racist regimes...Last I checked, Al Quaeda, and many fanatical groups are fighting because they don't like foreign invaders on their land, disrespecting their sovereignty. Just the same as Vietnam and Korea..
Therefore these "enemy combatants" are not even close to being afforded protection, because the protocol which would offer it to them is not ratified. Basically its a loophole, allowing them to be subject to torture, as we have seen.