This thread delivers.
Canadian exceptionalism, misunderstanding the 2A, misunderstanding what Americans can legally do with their owned firearms and a good dose of holier than thouism. Add in some bad statistics (looking at you VikB) and misunderstanding about whether America is a Democracy or not and what that means. But about what I would expect for NSMB talking about firearms and Americans. Subjects most Canadians are ignorant about IMO.
America is a different country, with a different cultural origin. Where Canadians stayed as happy subjects of the Crown (and are still generally happy to be subjects) Americans threw off the yoke. Everything from then on diverged their culture from ours. In the 1700's the folks who were white on this continent were not much different, whether they were North or South of the 49th parallel. Comparing Canada to the US is about as meaningful as comparing the US to Mexico, despite our 'common' language.
None of us up here generally 'get it' IMO, as the cultural differences are constantly reinforced (especially over the last 20-30 years up here from what I've seen and read). Canada has continued to push a civilian disarmament plan, where as Americans have gone the other way. Despite that gun culture (because of it?) homicide rates continue to fall in the US and Gun Culture 2.0 is racially diverse . Canadian gun owners are still culturally much more homogeneous - old white guys etc. In the States, firearms ownership is growing rapidly among young ethnically diverse urban dwellers, and they're not buying hunting rifles.
The streets don't actually run with blood down there - most deaths are suicides (60%) or gang related (22-27%). Accidental deaths run about 3% (<1000 per year VikB). That leaves between 10-15% (3200-4800 in 2011 #s) as what most of us would think of as interpersonal homicides. Avoid shooting yourself, don't deal drugs or hang out with dealers and you have a pretty slim chance of getting shot. Those figures were from 2011 but homicide rates are down about 50% from the 1990s, so pretty valid IMO. The endless news media cycle tries to persuade us that things are different with their constant coverage of murder and mayhem - if it bleeds it leads!
The 2A was written expressly with the intent to allow regular people to defend against a tyrannical government. They'd experienced that once already and knew what they were talking about. Syncro's point about a musket being different to an AR15 is a typical red herring. At the time of the War of Independence, many Americans were BETTER armed than the Redcoats - they had rifles which were more accurate than the muskets which were literally unable to hit a man outside of 50 yards - they didn't fight in big lines because they liked the symmetry. Against that were colonials who could often kill a man at 200 yards or more due to the better accuracy of their firearms. The Supreme Court in the US has actually ruled that NON military firearms are NOT covered by the 2A! Most folks don't know that. So owning something that is not an AR15 or derived from a military type firearm puts you at more jeopardy than owning a select fire assault rifle. Why would you expect to restrict people to a firearm that is less capable if you expect them to defend themselves against the government that you expect to try and tyrannize them. IMO that argument is usually made by people who say things like "Well defending yourself against the government is ridiculous, you could never do that." Or "governments never harm their own citizens!". Both of which are patently false to even a casual student of history. Disarmament is usually the first thing governments do before subjecting their citizens to violence.
Of course the Founders of the US were against democracy - because they understood that democracy is fickle mob rule and nothing more. Most people don't understand that we don't live in a democracy, so when they see stuff like was posted above they think that can be used to attack the intent of the founding of the USA, which is ridiculous.
Americans CAN NOT just shoot after a truck that has run them off the road as it speeds away. And that's not what the OP represented the PB question as. But it's no wonder that a Canadian might think that it's what is OK down there - as it suits everybody involved in disarmament to paint a picture of a lawless society with everybody blasting away at each other. Of course that goes to my point about the streets not generally running with blood. Depending on your State, you can't even necessarily shoot a violent home invader without suffering the consequences of punishment by trial. In some States in the US, if someone is breaking through your barricaded bedroom door screaming that they're going to rape and kill you, you STILL cannot shoot them through the door despite the obvious threat to your life. The US does not have universal 'Castle Doctrine' which is what many Canadians seem to think applies when they think of the States. Using your firearm to defend yourself IS permissible in Canadian law - just expect that you're going to spend years defending yourself in court, after you've defended yourself in fact. I did read a statistic recently that suggested that US burglars preferred empty homes compared to Canadian burglars due to the risk attendant to their crime in the US, but I can't find again it to reference it here.
To answer your question OP - I would use something like this from Hill People Gear - it wouldn't serve as much of a deterrent against rednecks but there's not much point carrying a pistol that isn't accessible when you need it. At the bottom of my Camelbak where it's settled after riding for a couple of hours is a pointless place for a pistol, but then so is carrying one on your hip. Open carry is dumb IMO and makes you the obvious target. With that said, it's unlikely that I would carry while mountain biking even in the US. I struggle with wanting to carry what friends consider essentials when riding up here, and expecting to add a pistol into that mix would probably double my load! Unless I was riding in an area that i thought I was likely to be targeted in, there would be no need. The best way to avoid being a victim is to avoid areas where you're more likely to be victimized. I'd be generally happy to carry concealed in the US outside of riding my bike - or swimming. probably wouldn't tuck a Glock in my speedos. Defensive gun use is a nebulous # but even on the low end is thought to run 500,000 per year (high end 3 MILLION) - instances when having a gun has prevented victimization, robbery or death. Canadians for good reason can't wrap their heads around that idea.
Edit: If any NSMBrs want to come shooting - drop me a line. Ammo's on me. Come and see how safe and regulated Canadian firearms owners are.