The speaker points to a gap in what we pay attention to. Bombs going off far away become news, partly because the victims "look just like me." Meanwhile, in America, huge amounts of explosives are used every day to blow up mountains, apparently to get coal, whose burning is what "keeps us cool." That goes unreported because it happens daily, has no clear enemy, and kills slowly, mostly people who are poor.
The poem then turns to the heat itself. News anchors, "righteous and well-coiffed as fallen angels," act outraged at the sun but never ask why it's so hot. The repeated line about burning the mountains' "black hearts" closes the poem like an accusation nobody wants to hear.
The mood is angry but controlled. The speaker's tone is dry and sarcastic, and the repetition of "Meanwhile in America" builds a steady, weary pressure. The poem suggests we are harming ourselves while looking elsewhere.