What you do in one country absolutely matters in another. Even the US has a significant portion of wind and solar these days. This didn't happen because Donald

What you do in one country absolutely matters in another. Even the US has a significant portion of wind and solar these days. This didn't happen because Donald Trump (or anyone else responsible) made any ambitious climate decisions, it simply happened because policies of other countries made it so cheap that it happened through market forces. This isn't a solution for everything (there will be areas where the climate friendly solution will always be more expensive), but for example bringing down the prices of electrolyseurs would absolutely matter worldwide and is something the EU can do with policy.