A German submarine sank the American battleship USS Texas on Friday, June 20, 1941. On Monday, June 23, 1941, Congress declared war on Germany, by a 387 to 48 margin in the House and 84 to 12 margin in the Senate. On June 24. 1941, Germany and Italy declared war on the US. Later that same day, Congress declared war on Italy.
On December 7. 1941, Japan declared war on the US and the UK and attacked American and British bases around South East Asia and the Pacific. With the state of high alert, the radar report of incoming planes at Pearl Harbor was taken seriously. The Japanese air attack was met in the sky by American planes. Word was quickly dispatched to American and British bases who began evacuating their fleets and putting their air forces in the sky. The Commonwealth and US fleets escaped largely unharmed. On December the US and UK declared war on Japan. In the American Congress the vote was 96-0 in the Senate and 434 -1 in the House. In March off 1942, US reinforcements landed on the Philippines. As part of the mobilization process in 1941. The Filipino Army had been fully supplied and they were able to hold off the Japanese attack. By May 1942, the Japanese had been driven from the Philippines. In July Allied forces were built up in New Guinea and landed in Guadalcanal. In November, Allied forces landed in Burma and the Gilbert Islands.
Operation Torch on June 7. 1942 began the North African campaign. The peace deal with Vichy commander Francois Darlan on June 10. 1942 ended the fighting in Algeria and Morocco. Allied forces moved on to Tunisia and secured it by May 27, 1942. In June 1942, Allied forces invaded Libya and quickly over ran the Italian colony by the end of July. In August, the invading Allies attacked German forces in Egypt. On September 2, 1942, the last German forces in Africa surrendered. On November 8, 1942, Allied forces invaded Sicily. Mussolini was overthrown on November 22, 1942. On December 3, 1942, the new Italian government declared war on Germany. By the new year German troops had secured control of most of the Italian peninsula. The Italian front became a bloody quagmire.
1943 brought impressive victories to the Allies. In the Pacific the great success was the conquest of the Mariana Islands in July. Bombing of the Japanese home islands would begin on November 28. 1943. In Europe, the WAllies would invade Normandy on October 6. 1943.
1944 would see the final Allied victories. The good news began with the victory in Iwo Jima in February 1944. April to June 1944 saw the successful invasion of Okinawa. In August 1944. WAllied troops would hurry into Poland to rescue the Warsaw rebels. They liberated Warsaw on August 27, 1944. The WAllies had already liberated Prague on August 23. 1944. Germany would surrender on September 6, 1944. The USSR would declare war on Japan on December 6, 1944. The Japanese Empire would surrender on December 16, 1944.
The changes brought by this TL primarily effects two countries. Poland is divided into two separate countries until 1990, when the citizens of Communist East Poland vote to rejoin West Poland. In 1945,Czechoslaviak comes to an end. There is a not so velvet divorce as Communist controlled Slovakia breaks away. Throughout the Cold War. West Poland and The Czech Republic are the front line nations of NATO. In another change, they are host to most of the US military bases. So if you are the child of a German and a member of the American armed forces, you may have a different heritage.
Another possible change is that Franklin Roosevelt may live longer. Probably not all that much longer.