I was wondering, what is it about the history and culture of the USA that has lead to a very different firearms culture than exists in the UK?
Big, empty country with tenuous (at best) protection from the central authorities for the majority of our existence, and plagued by violent partisans for much of that time (natives as well as bandits). I'm sure it's hard to grasp for Old World residents where civilization has existed since the dawn of history, but Americans were truly on their own when it came to defense at the personal, local, and state levels for a long, long time. The reason we had militia prior to the Revolution is because the official Royal army/navy/constabulary were unable to provide a persistent deterrent to attack way out in the colonies. The reason individuals needed firearms of peak military effectiveness was because there wasn't even a militia out on the frontier, where the threats were not animals but men as cunning as themselves waging insurgent warfare.
Europe has had pacified lands (defined by a significant government oversight of some kind) for millennia that reduced the need for such distributed defenses among the populace, and highly centralized political structures going back to feudalism dominated, reducing the desire for such distributed responsibilities as well. America was practically nomadic for centuries as the continent was explored & settled by consecutive waves of homesteaders, consistently outrunning the capacity of the official authorities to protect them (or even manage them in general). This extended to every level of government, to include the Crown itself with the long-standing policy of 'salutary neglect' prior to the revolution that left the colonists to more or less run themselves autonomously, with comparatively weak protection from piracy, natives, and other foreign powers all the while (which is why the sudden demands from the Crown that the colonists fund the French & Indian War debt was so offensive)
Right around the time America became 'settled' --the turn of last century, the 'Dying West'-- was when this Gun Control fad, and many Progressive ideals along with them, suddenly came of interest. They had been pursued to their (racist) conclusions in the crime-ridden slums of the big cities already in most cases, but the hinterlands had mostly resisted for the aforementioned practical reasons. As with all social changes, there were malcontents who resisted them, which is where the modern gun rights movement is descended from. Our side is resurgent once again, primarily because of the practical realities of living in a dangerous world, where the police cannot always be there to protect you, violent criminals continue to exist in some capacity, and bloodthirsty foreign powers are out for our blood (these three things have always existed & always will, but until recently our government has been pretty good at convincing us they'd taken care of them)
I'm certain that thousands of years ago, when denizens of the Isle were still painted blue & worshiping the seasons, and fighting off rival tribes & wild beasts, that there was a similar attitude toward whatever clubs & spears they held. But eventually, feudal gangs defined their turf through powerful weaponry, and forcibly disarmed the peasantry and extorted their produce in exchange for 'protection' against identical feudal gangs from surrounding areas. Couple hundred years of myth and domination later, and you have the royal hierarchies that all the various European states (and Asian/etc for that matter) descend from.
TCB