Thank you for your question, mil.
As a gun-obsessed American myself, I’ll attempt to answer this to the best of my ability.
As other answerers have said, American history is very much based on an individualistic, frontiersman ideology. In the early days of the Puritan settlements, to the colonies, and well into modern American history, if you didn’t shoot, you didn’t eat, and you were often required to look out for yourself and others (especially in the vast rural areas of the US that still exist to this day). Guns just happened to be the best tools for this job, plus people have always needed a way to defend themselves from wild animals as well as certain ne’er-do-wells that happened to permeate the American frontiers.
This sort of idea of self-sufficiency via the gun stuck, and we have the modern “gun culture.”
Many people, particularly those abroad, tend to equate guns and shooting with violence and crime, and thus look on us gun-owning Americans as barbaric or uncivilized at times. As a member of the “gun culture” I can tell you that, more often than not, this isn’t the case. As a history buff (I’m specializing in history in school) I can tell you that guns for me are about history. I own several, and for me, they do not represent violence or death. They are mechanical devices that have played an important role in shaping world history, and they happen to be incredibly fun to shoot and collect. My guns have never gotten up on their own and shot up schools, and I have no desire to use them for violent purposes. They are just objects that I find interesting and beautiful, and my feelings about them are best summed up in this quote by William Morris:
“Have nothing in your house that you do not know to be useful, or believe to be beautiful”
Also, to answer the last part of you question, you may find this link useful: http://en.wikipedia.org/wiki/Gun_laws_in_the_United_States_(by_state)
Hope that helps, feel free to ask if you have any other questions/comments.