The whole reason Japan started their program of military expansion in the first place was to guarantee access to natural resource, e.g., petroleum, needed by their industry.
By 1943 Japan was facing chronic shortages of petroleum products, rubber and other essential supplies because of interdiction by the US Navy's "Silent Service" (submarine force). And that was before Japan lost most of her navy, most of her large transport ships (by 1945 Japan was reduced to using mostly small wooden transport ships) the Phillipines, Iwo Jima and Okinawa (which while in Japanese hands could be used to operate aircraft to give Japanese shipping some protection from the US Navy).
It is unlikely that Japan could have done much more than feed itself after 1945.