> should we take care of our own (American) citizens first?

We should take care of the planet. We all live on it and catastrophic heat waves and extreme weather are not polite and do not respect the thick black lines we've drawn on maps.

For avoidance of doubt, I am absolutely saying that if those of us who are citizens or residents of the United States, European Union (with or without the United Kingdom), Australia, Canada, Japan, and anywhere else anyone might think of needs to take a hit to our net incomes and economic circumstances in order to keep the planet habitable, I am all for it.