The concrete planning for "how to deploy the atomic bomb" was not started until late 1944, and didn't really ramp up until spring 1945. By that point they knew that a) the bomb wouldn't be ready until late summer 1945, and b) Germany was going to be out of the picture by then.

So there was really no other country contemplated in a serious way.

This is different from asking what might have been done if the schedule of the bombs was different. There are some indications that if the bomb had been ready in 1944, Roosevelt was prepared to consider using it against Germany. But it wasn't, so the point was a moot one.