No doubt it seem that way to you because you haven't done any research into the matter.
Hitler had a number of reasons for declaring war on the USA and since you seem to have missed them the last several times they were spelled out let's recap:
1 - He hoped Japan would reciprocate by declaring war on the USSR.
2 - The US was already fighting an undeclared war in the Atlantic with US ships engaging U-Boats, the
USS Reuben James was sunk on the 31st of October 1941, over a month
before Pearl Harbour.
3 - Doenitz was arguing that the U-Boats had to target shipping in US coastal waters where they were easier to locate and far more vulnerable. They launched this campaign
'Operation Drumbeat' within days of the German declaration of war. They saw huge success at first despite limited U-Boat numbers and this is referred to as the 'Second Happy Time' for the U-Boats.
4 - Hitler had decided in his own twisted world view that Roosevelt was the arch-champion of the Jewish Conspiracy. War with the US was inevitable, better to fight sooner rather than later when the US would be much stronger.
Hitler was right about one thing, war with the USA was all but inevitable for Germany at some point, he tried to seize the initiative with the declaration on 11th December. He utterly miscalculated the US response and the speed with which it could build up its armed forces, but in no way was it a spur of the moment decision or an example of Hitler issuing 'insane' orders.