I can totally see gun rights advocates in the US saying something along the lines of: 'If people were allowed to privately own guns in the UK, the Rage outbreak could have been easily nipped in the bud by having just a SINGLE security guard at the Cambridge lab being armed!'
I was reminded of post I once saw on another forum that I will be quoting, it is not related to "28 Days Later", but I do think that it applies to the situation perfectly:
'The primary industry's in the US around this time would most likely be guns, bulletproof bibles, and of course SUV's. Think of it as the constant cycle of American preparation after disasters. After Katrina everybody in Texas bought canned food and flood insurance, after 9-11 we bought Gas Masks and Duct Tape, after Obama got elected everyone has been buying all the guns and ammunition they can find. To this day a large percentage of Americans are still buying all this crap. The point is that when the American people are in a constant state of distress, they take capitalism by the arm and spend money on a way to alleviate their nerves. [...]If you do not know what lengths the American people will go to for the safety of their family and property...'
In the case of the 28 Days Later universe, the United States would have just witnessed helplessly on TV a close ally that the country has close cultural, political, and economic ties to literally getting almost wiped out within a single month, a country that many people would have either personally visited, knew someone from, or is at least somewhat intimately familiar with. I fully expect not just gun ownership, but full-scale zombie apocalypse style doomsdays prepping will be in fashion for at least until the mid-2010s.