Could the US have beat Japan without the atom bomb?

Hindsight is always 20-20. With that said, Japan's military resources had been stretched to the limits by its multi-front war that Japan itself created. Based on the US's population, the safety of its industrial base and its advanced technology, Japan had no chance of defeating the US. It vastly underestimated the power of the US. Japan was not alone in bad estimates. Hitler also underestimated the power of the US. He would have been wiser to never involve the US in the European fronts of WW 2.

In fact, Hitler's declaration of war, to basically help Japan was foolish in that Japan refused to attack the USSR based on a flimsy treaty the two dictatorships had with each other. Japan and the USSR kept their treaty of nonaggression until Japan was basically out of the war. Then Stalin attacked the mortally wounded Japan. Hitler made a huge error and so did japan.