Actually, there was nothing which impeded a German settlement with Poland and integration of Poland into the Axis as Romania, Hungary, and Slovakia were beyond Polish intransigence. Polish foreign policy was effectively dominated by an authoritarian military clique which rejected any notion of settlement with German officials, as well as boasting of the Polish Army entering Berlin in three weeks. To say that the Polish elite desired a peaceful settlement is a historical distortion. The Second Polish Republic was at the time an extremely aggressive and hostile entity, most foolishly toward two powers, NS Germany and the Soviet Union, which had every means at their disposal to see it smashed as a state. That it met its historical fate of facing a joint invasion and subsequently suffering occupation and the privations of war is nothing less than extremely predictable.
The Second Polish Republic also was extremely anti-Semitic, a boastful, weak kitten in foreign policy, whose army was still mounted on horses using cavalry against tanks in 1939. Their intransigence would eventually lead to them disappearing from the map of Europe from 1939 to the end of the Cold War essentially. Its two greatest enemies were Germany and the USSR. That England and France went to war with Germany to protect this backward, anti-Semantic, antiquated republic is surprising. When major nations fall out, it is better for smaller ones to simply fall in line. Poland had no chance of surviving, and the German claim on the Danzeg Corridor was one of portions of the Versailles Treaty Hitler needed to eliminate, mainly to insure an uninterrupted flow of Swedish iron ore to the German steel mills.
What is really surprising about the 1941 start for America in the war at Pearl Harbor, is that Hitler decided to declare war on us, but didn't insist on quid pro quo of Japan declaring war on the Soviet Union, which was engaged in a mighty struggle which if Germany won, would have ended the war. In control of China, a Japanese attack from the opposite direction against the Soviets could easily have succeeded, and broke the Russian spirit, and won the war quickly, before America had time to regroup. That would have left Germany and Japan to deal with America and England alone. One of the most unusual stories of World War II, is American Lend Lease convoys sailing to Russia, through Japanese waters, without ever being attacked by the Japanese navy.
The Japanese had no plans for conquest against America or Britain, they just wanted their Greater Asian Co-Prosperity Sphere, and probably would have been successful at it if their army hadn't been so harsh on native populations in China, Korea, Burma, Philippines, etc. They eliminated American naval power in the Orient for a year with the Pearl Harbor attack, eventually, all those battleships sunk, except the Arizona, would be repaired and fight again later in the Pacific War. They also eliminated British Naval power within days of Pearl Harbor, catching the two British battleships, Prince of Wales and Repulse, based in Singapore, out in the open and sinking them with air attacks. They knocked American infantry and air power out at Clark Field in the Philippines the day after Pearl Harbor, catching Douglas MacArthur's American planes (200), all lined up wing-tip to wing-tip, for easy destruction. That made the Philippines indefensible, although American and Philippine forces held out for six months on Bataan and Corrigidor, delaying Japanese expansion plans.
The Pearl Harbor attack on America was a huge mistake. Roosevelt would never have been able to send the American navy at Pearl Harbor sailing 12,000 miles west to Japanese waters based on their invasion of China, Korea or the Philippines. Public opinion would never have approved of it. Up until Pearl Harbor, the American public was completely neutral regarding entering the war. After Pearl Harbor, the Yanks were riled up, enlisting in droves, ready to fight the "Yellow Peril" for revenge. Roosevelt was a master and knew enough to trust the war policies to experienced military leaders, unlike Hitler, and Churchill for that matter, who were military meddlers. Admiral King with the U.S. Navy, and Chief of Staff George C. Marshal performed brilliantly during World War II. Marshal's decision to persuade Roosevelt that Germany First was necessary, and let the Pacific theater against Japan wait, was the main reason for the Nazi's defeat, along with sending American armaments to the USSR. The idea that America was able to recruit and create an entire army of GI's (General Issue) soldiers, to tackle the German's in World War II, and never loose a battle to Germany in two world wars was amazing, if one ignores the brush at Kasserine Pass in Africa. On December 6, 1941, American public opinion opposed any active involvement in that war. On December 8, 1941, America was all in..........Stan........