What you write here is the letter of the law, but it does not reflect the reality of US foreign policy since 1970. A simple example: has Congress declared war to allow the US military to enter Syria? The justification used (I believe, though I could be corrected) would be the general War on Terror declaration back under Bush II, but there has never been any congressional debate that I have seen to discuss militarily occupying Syrian soil. The military - directed by the president - simply did it, and nobody questioned it. The idea that the US is operating under the framework of the law as written is a fiction. They use it when it is useful to them, and ignore it when it doesn't.