This just in, belligerent nations also understand the value of global virtue-signalling.
China and India are the ONLY ones that matter in terms of global emissions. They still have 2 billion people between them that are dirt-poor and have yet to take part in their national economy in any meaningful way. Right now, with only 1/4 of their populations economically active, they account for over 37% of TOTAL GLOBAL EMISSIONS.
The US, with 350m people and 99% economic engagement accounts for 16% and decreasing. China and India will continue growing, and their overall percentage will increase dramatically in just 5 years.
Per-capita use isn't an argument either, sure the US has higher per-capita use, but if you look at the actual number of economically engaged people in India and China, their per-capita use is actually higher than the US, it's just averaged out across the other 2 billion people that aren't responsible for anything more than cookfire smoke - no cars, no consumer goods, no roads, no airplane travel, because they can't afford any of those luxuries.
The US was committed to 25%+ reduction in just 7 years. China and India's pledges were next to nothing - no percentages of reductions, just vague promises to spend more on renewables and the (non-binding) promise to do 'something' by 2030. That's a pretty one-sided agreement, and the 25%+ reduction in the US would do absolutely nothing in the long-term for the world, but would hurt the US economy.