From recent memory, the pandemic came closest to that kind of across-the-board threat. Early on in the pandemic I worked in getting equipment into hospitals in three states in the US where I live and later on in 25 other countries. It was amazing how zero-sum the response was to the situation, across every governmental system, large and small
I saw US states poaching ventilators from other states and countries stealing truckloads of ventilators from other countries. I saw countries' customs departments hold up medical equipment for bribes while their citizens died,, private companies hoarding and scalping off supplies and all that resulted in an incredible amount of preventable death and suffering. Across all of this, the response from state to state and country to country was incredibly varied. Everyone had a different opinion about the best course of action, and groups making a coordinated response were only as large as their social ties allowed You could call it tribal or expedient or diverse depending on how you look at it but there was exceedingly little cooperation between tribes even at the smallest level.

It feels a bit callous to call the pandemic a minor emergency, but it's certainly not the sort of threat that threatens the survival of our species, or even a significant percentage of the people on the planet (compared to, say, nuclear war, or an asteroid strike, or a more lethal disease). Still, if you treat this past emergency as an indicator of how our world acts in a crisis, don't expect a lot of cooperation between socially distant groups, cultures, or countries. More like Don't Look Up rather than Independence Day. Maybe a more serious emergency would inspire people to cooperate, but my feeling is, if you can't ride with training wheels, you probably won't do that great on a big kid bike.