Guns

Amendment II: "A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed."

The wording of this amendment is the best explanation I can give as to why the US is politically unable to institute stricter, more rational gun control laws. When taken in the context of the political and cultural realities of today, this amendement can most certainly be interpreted to give great freedom of the citizenry to pack heat and be ready to kill anything that moves to protect said personal space.
In this day and age, the primary philosophical basis for arguments of freedom and rights is "the state" vs the individual. This is not the context that existed in the US during the drafting, debate and ratification of this Bill. In those days, the primary philosophical question was what rights the States had over the central national government. Hence, the context of the Second Amendment was referring to the armies maintained by individual States (aka "the people").
The looser Articles of Confederation that preceded the Constitution had a very weak national governemnt, which was completely secondary to the State governments.
The legal rights of people to pack weapons giving the the power to kill each other with the flick of a finger is an accident of history. It is an accident of history that will not be corrected in my lifetime. That's a bummer.