A Chinese attack on Taiwan would significantly impact Japan and the U.S. due to Taiwan's strategic location at a crucial maritime crossroads. Control of Taiwan would allow China to dominate regional waterways, project power into the Pacific, and potentially break out of the First Island Chain. Japan's security alliance with the U.S. would be tested, as American intervention would likely require Japanese support. The geographic proximity of Japan's Ryukyu Islands to Taiwan further complicates the situation.