There are huge differences, mainly economic and political rather than technical. CFCs were relatively easy to replace with substitutes that were just as effective and ultimately not that much more expensive. Also, major American chemical manufacturers (like DuPont and Dow) were well positioned to dominate the replacement market, so they eventually supported the policy change. As a result, the US was a global leader on ozone policy, even under the Reagan administration. It was fairly easy to build an international consensus with those factors in play. The cost gap between carbon and no carbon sources of energy is much bigger…although it has shrunk considerably for some applications (like renewables for baseload power), there is still a pretty big gap for things like peak power, transport, and industrial heating. Also, fossil fuel producers have trillions of capital tied up in long term projects, and they are not going to let that capital be stranded without a massive fight. As a result, the US is a laggard on climate change rather than a leader, and US leadership is still really important. (It’s probably less important than during the ozone situation in the 1980s…the EU has stepped up a lot on climate. But given the size of the US economy and the fact that other large economies like Russia and China basically need to be forced into energy transition, the absence of US leadership is pretty devastating.)