If they cut off water, power, healthcare and food and distribute them to the compliant, it will take 5 days to turn 98%. Then they'll use the self identified extremely compliant to hunt down the rest.
Guns won't really help. The new LRAD sonic weapons and heat based ADS weapons will render them useless. The few who planned ahead will be easily exposed and rooted out by their dehydrated, starving neighbors. Their indefinite detention and unexplained deaths will not be mentioned by anyone.
It won't be a takeover either, as such, it will be a "reluctant response" to either a "terrorist attack" or a disease or toxin, or a bomb, or domestic terrorism by racists, or something like that for us to all get behind and sacrifice together.
The press won't need to be muzzled or made compliant. That already happened.
Canada is no processing applications right now, as their offices are overwhelmed. Don't believe me? Call them and see.
Of course this is all hypothetical, but if those in power chose to go this route, it would be very easy to do so.
All representative democracies eventually become oligarchies
http://en.wikipedia.org/wiki/Iron_Law_of_Oligarchy