I grew up in Mississippi, and I sometimes live in Manila, Philippines. Manila is a single city with something like five times the total population of my home state of Mississippi, grinding poverty like nothing we've seen in America since the Depression, rampant drug trade, and governmental corruption that would make Boss Tweed blush. But even though one would think this combination of overpopulation and poverty and corruption would be toxic enough lead to high levels of violence and homicide, Manila has a lower homicide rate than Mississippi. But then, Mississippi - which, for all its problems, has LESS corrupt and ineffective government than Manila, LESS extreme poverty, FEWER gangs and factions, and MUCH less drug trade than Manila - has a far, far higher rate of gun ownership.
What you left out in your list above is the degree to which gun ownership is regulated. Two nations may have significantly different gun ownership rates, but if they both regulate those guns to the same degree, you may still get similar homicide rates. You compared Canada to England. Most people in highly-urbanized England see no need for gun ownership, and so the gun ownership is less. Canada's gun laws - while significantly less restrictive than those in England - are still much more restrictive than in red-state America, since Canada requires universal background checks and registration of all firearms - and assault weapons are illegal there IIRC. But Canada has a much higher gun ownership rate than England because England is highly urbanized, whereas Canada is one of the two most rural first-world nations on the planet - and having grown up in Mississippi, I have a real appreciation of the need - need! - for firearms in rural areas. But since Canada DOES require background checks and registration and restricts firearms that have no place outside the military - and their conservatives aren't filled with fear that the guv'mint's a-sendin' those black helicopters to come confiscate their guns - their rate is roughly equal to England's.
Y'know, I just realized that the city of Metro Manila itself has over half - and perhaps two-thirds - the entire population of Canada? Man....