When an invasion of Japan replaces the atomic bombs

Could the United States have invaded Japan instead of dropping atomic bombs?

Yes if the weapons failed to become usable; otherwise American leaders would use them rather than proceed directly to invasion.

The counterfactual changes the war by making the atomic weapons fail in testing or development. Under that premise, the United States must continue toward an invasion of Japan. Once functioning bombs were available, they became the leading alternative to that invasion and would be used. This short exchange offers a counterfactual judgment rather than a full survey of the wider historical debate over surrender and casualties.