What brought the Pacific War to an end? The combination of the destruction of the Japanese Navy, the failure of Japan to win in China, the repeatedly-demonstrated ability of the US Marines and Army to defeat the Japanese on land, the large-scale (conventional) bombing of Japanese cities, the atomic bombings, and the Soviet invasion of Manchuria.

Could enough of these be achieved earlier in time by enough to result in a Japanese surrender before VE-Day? The Soviet invasion was not going to occur before the end of the war in Europe (which was keeping the Soviet Union very busy). The atomic bombs were not going to be ready much earlier than they were. The destruction of the Japanese Navy had to wait to the US Navy to be built to a sufficient strength, Japanese naval air power to be eroded by attrition (with the air battles in the Solomons doing much of this, and the Battle of the Philippine Sea killing many of the remaining skilled and experienced aircrew). This last was perhaps achieved earlier than expected due to comprehensive Japanese defeat at Midway, which in turn would have been more difficult if Shokaku and Zuikaku weren't out-of-action due to damage and losses in the Battle of the Coral Sea.

An earlier bombing campaign against Japan would have required faster island-hopping by US forces through the Pacific, or secure bases with sufficient supply in China. As it was, the island-hopping required the buid-up of the US Navy to support the various invasions, so this would be unlikely to be achievable much more quickly.

This leaves obtaining safe bases in China as the only realistic option. This would have required securing the land supply routes from India through Burma to China, and the movement of enough US forces into China to protect air bases. Supplying China by air when the land route was cut was sufficient to keep Nationalist China in the war (just!), but was not able to supply a serious China-based bombing campaign against Japan. Keeping the land route open and protecting bases in China would have required a much larger commitment of US ground and air forces to Burma and China than was possible with priority given to Europe and the defeat of Germany. Therefore, the only real possibility would have been if the defeat of Japan was given priority over the defeat of Germany (and Italy, and other German allies). However, just as Italy did not turn out to be a quick path to the defeat of Germany in Europe, Burma was hardly the "soft underbelly" of China, and this option could easily have failed to deliver a faster victory. Even the total defeat of Japan in China, and convention bombing of Japan from China might not have resulted in Japanese surrender before atomic bombs and Soviet entry into the Pacific War.

Another possible path to China would have been an amphibious landing on the Chinese coast. This would also have required Pacific priority for large enough forces to be available, erosion of Japanese naval power, and would be too dangerous if sea routes for supply were not secure.

On the other hand, a US priority on victory in the Pacific could easily have slowed victory in Europe, making it possible to achieve victory in the Pacific first.