Canda, UK, Australian not dictatorships despite gun control

The NRA assures us that Barrack Obama is gonna "take your gun" and that this will be followed, almost instantaneously, by Nazi-style concentration camps and genocide. Of course, they already assured us that this would happen in Obama's first term.  Now they are absolutely certain that it will happen in the second term.  But there seems to be a problem with their theory in general.  If collecting guns leads directly to tyranny and concentration camps, then why hasn't this happened in Canada, the UK, or Australia.  They all have public health care systems (Obamacare/socialized medicine) as well, I might add.  However, we see no gas chambers or crematoriums.  In fact, Canada, the UK, and Australia, despite having gun control and public health care, which would be branded "communism" by Tea Party fanatics, actually have had "conservative" government of late.  But they haven't always had conservative governments, and they still have higher taxes, both in general, and on the wealthy than are found in the US...all without a dictatorship, or a modern-day holocaust, or cadres of gun-toting civilians to keep the government from being "oppressive".  So what gives?  Why is it that these countries are not dictatorships when the citizens are not armed to the teeth?