With 90% of US population gone that would mean the rest of the world would be on that so called “level playing field”. Everyone would now have a great shot at success.
If they really believe in AGW they should fear such an outcome.
All of the unburied dead would generate huge amounts of CO2 and methane as the bodies decomposed. If Global Warming is truly caused by these gases accumulating in the atmosphere such a global catastrophe would surely bring it on with a vengeance.
Besides the decomposing bodies urban fires would spread unchecked because fire departments would not be able to fight them due to failed municipal water systems.
The unrestrained collapse of civilization would be an environmental disaster of unimaginable proportions.
Except for the inconvenient detail called food. No food exports. No foreign aid. No consumer economy keeping 3rd work countries engaged exchanging cheap labor for food and income. A level playing field with everyone neck deep in excrement. Any effort to avoid death would be a "success".