What if the United States invaded Manchuria after Pearl Harbor?

Inspirations:

• Abolitionist, Not Pro-Life
• Abolitionists Rising's Norman Statement

Suppose in a parallel universe, Franklin D. Roosevelt suddenly decided that the island hopping campaign utilized in the OTL was "regulating Japanese war atrocities" and "disrespectful to those slain at Pearl Harbor" and, upon declaring war on Japan post-Pearl Harbor, ordered a military mobilization with the intention to invade Manchuria and use it as a beachhead to attack the Japanese mainland.

He rationalizes this through a rather interesting interpretation of the Christian Bible, saying that "God forbade Moses from using incremental measures to free the slaves from Egypt, and now God forbids the incremental capturing of Japanese-occupied territories as part of our campaign against the Empire of Japan as a compromise with the forces of evil. We must exact immediate retribution against Japan, and we will do it by taking Manchuria!"

And so, the decision is made to mobilize for an invasion of Manchuria, intending to seize it from the Japanese and use it as a staging ground for the invasion of Japan itself.

Would the US realistically have the manpower to pull off an invasion of Manchuria rather than using the Island Hopping method?