Yes, that. But also that these different externalities will have different responses to reduction at scale, which also impacts how effective action on a more "personal" level really is.
For example the OP was talking about plastic. A 2% reduction in plastic waste has a clear benefit, because any amount of plastic reduction is a bonus. However it is not clear that a 5% reduction in CO2 emissions due to Americans driving their cars less will have any meaningful difference when it comes to climate change.
Still not understanding you, if you meant "a 2% reduction in plastic waste in country A" is of no global benefit if there's a comparable increase in country B (assuming their disposal is roughly equally bad for the environment globally, since only 9% of plastic globally is recycled). So I assume you meant "a 2% reduction in plastic waste, globally". But then the same criticism applies to country-level reduction in CO2 emissions.
Anyway, maybe the second Trump admin will exit the Paris Accord again, putting strain on China and India participating, so climate summits will be weaker till 2029 (earliest).
Likely the domestic economic impact (on the US) of major climate-related events will have more influence on US policy than international. e.g. whether one of the many causal factors to the huge 2025 LA fires was climate change; or California's water setup where Senior Drawing Rights legally predating the existence of the state of CA allow agribusiness essential unlimited water use to grow pistachios in a semidesert during a drought, or bottle and export artesian water. As well as all the other more proximate causes. Anyway, expect a long and politicized fight between state, federal, city and insurers about the LA fire root-causes, liability and federal compensation. Especially given there's a plan to weaken or abolish the US EPA at the same time.
Ditto, expect nation-level debates (in OECD countries) reappraising whether nuclear (alongside fossil-fuel and renewable) is considered safe, desirable and necessary and how that affects/limits GDP growth, and whether datacenters and AI continue to be seen as a proxy for GDP growth, or whether that assumption breaks down some year soon.
