Congress has created and funded a huge peacetime military that has substantial abilities to wage offensive operations, and it has not placed restrictions on the use of that military or the funds to support it, because it would rather let the president take the political risks in deciding on war. If Congress wanted to play a role in restricting war, it could - it simply does not want to. But we should not mistake a failure of political will for a violation of the Constitution.
I would distinguish between Donald Trump and the United States of America. Although he is president, he does not speak for the country on the climate change, and that was vividly illustrated in the aftermath of his speech pulling the US out of the Paris Agreement. Almost immediately, not only did the rest of the world double down on its commitments, but also here in this country, governors, mayors, business leaders, they said, we're still in the Paris Agreement, and they're doubling down. A lot of cities have now made a decision to go 100% renewable energy.