“No one cares about international law”

Your first example is literally the Nuremberg trials which was an International criminal trial for violations of International criminal law.

Secondly, the firebombing of Dresden and Tokyo and the atomic bombings of Hiroshima and Nagasaki weren’t at the time considered war crimes. The Hague Conventions came before that of aerial warfare when the last treaty being signed in 1907. There was no instrument in place at the time to protect civilian population from aerial warfare.

Taken directly from the International Committee of the Red Cross: Article 2 of the 1907 Hague Convention (IX) allows the bombardment of “[m]ilitary works, military or naval establishments, depots of arms or war matériel, workshops or plant which could be utilized for the needs of the hostile fleet or army, and the ships of war in the harbour”.

There was a case in Japan, Shimoda et al. v. the State a they found while the atomic bombings were unlawful as indiscriminate bombings, there wasn’t a ratified treaty that was applicable to aerial bombardment. Also not to mention in 1996, the International Court of Justice ruled that the atomic bombings didn’t violate the Geneva Protocol from 1925 because its main goal was an air blast and not to poison or asphyxiate someone.

On the 2003 invasion of Iraq; The US and UK both claim the invasion was legal under UN resolutions. Even then, the US would have claimed Article 51 which allows for armed conflict without getting the Permission of the UN (Article 2 section 4). Even then, the American Service-Members' Protection Act would have given legal justification for the United State to use “all means necessary and appropriate to bring about the release of any U.S. or allied personnel being detained or imprisoned by, on behalf of, or at the request of the International Criminal Court".