Yeah, I think that really it wouldn't be the "global community" that ends up saving the world in an asteroid impact scenario.
It would likely be an organization that could operate on its own without endless committees. Say, the Chinese space agency, or SpaceX, or the Indian space agency. Someone would decide to just do it, without getting the whole world's approval for the mission. Then the whole world would complain that the effort was made without any international cooperation or oversight. And the organization that literally saved the world would get chewed out by everyone because inevitably the plan will not have worked perfectly.
But I'm not worried, because even billionaires don't want to die. Someone would do something.