In the 1960's America launched massive military attacks on Vietnam, a war as epic and bloody as WW2. About 3 million died, refugees 1 million (Vietnam, Laos, Cambodia). Canada acted and took in many thousands. I  helped out by sponsoring a family of 5. But we did not 'lead a global response'. That's because we did not create this war, did not participate in it. Our responsibility was humanitarian, not leadership. Leadership responsibility belongs to those who started war, who participated in it. 

Ditto on the current refugee crisis in the Middle East. American president GW Bush started it. American president Obama continued with it, sustained it, even expanded it to Libya and Syria. 

Let America and its war partners handle it. They do have a lot of money, a lot of compassion, right?