Sure, screw the 28,000+ US Service Personnel that are stationed in South Korea.
We are free to move them out if we are not comfortable with the danger they are in. Even if that wasn't the case, are you saying we should screw the 14,000,000 citizens of the country we are in so that we don't screw the 28,000 military personal we chose to station there?
Plus the itsy bitty issue of those 28K troops not really being at risk unless full scale war breaks out, in which case we will reduce NK to ruble. If we start it, troops still at risk and we still reduce NK to ruble but we are responsible for starting a war that will likely lead to the capital city of our close allies being blown to hell.
If Canada places troops in LA and then thinks those troops are at risk from Mexican forces it isn't Canada's call if WE go to war or not, especially if the risk is LA being blown to hell.
They are our allies and we should back their play but make no mistake, it should be THEIR play to make. Get back to me when they start shelling a US city or sinking US Navy ships.