USA has the largest footprint
No one be fooled. Speaking as an American citizen, it is the USA and our political and business wranglings that have led the world to the brink of extinction.
It is our fault in nearly every way, from the dirty energy technologies being utilized to the consumer cultures accelerating their use.
Ironically, we also hold the technological keys to saving the planet through some combination of nuclear, renewables, batteries, fuel cells, and bio fuels.
My mitigation plan is 2 step:
Short/Medium Term:
A Nuclear-Methanol economy, where gen iv+ nuclear like LFTRs produce most of the consumable electricity and gasoline and diesel liquid fossil fuels are replaced by methanol produced large scale via industrial anaeobic digesters, as it would take a minimal retrofitting of current engine and fuel distributing infrastructure to make this work.
Medium/Long Term:
Renewable-Battery economy, where high efficiency renewables (photovoltaics, fluid turbines of all types, hydro of all types, geo thermal, etc.) are leveraged in combination with both smart-grid-level and node-level (local) high efficiency battery / fuel cell storage.
Of course, renewables will be utilized and evolving during the first phase (just to a smaller extent while the technology is maturing).