If Canada were developing a nuclear weapon that the US opposed, would you favor attacking even though millions of American lives would be at risk from conventional artillery and missiles (Seattle, Portland, San Francisco)? That's what all prior presidents have faced in a different area of the world. 
You do know Pakistan and India have nuclear capabilities? Most Americans don't and sleep very well. Pakistan, as I'm sure you know, is no great friend. Most of the time, neither is India. Sometimes, you cannot police the world. If you try (Vietnam, Iraq) you become the problem, killing millions yourself.