now I will largely agree with you here however there are a couple situations to look at. in the south pacific where much of the fighting was in rain forests and swamps things like P51s, tanks and artillery were largely irrelevant. the heaviest thing you could post were machine guns. had the Japanese adopted a semi auto rifle then the entire south pacific campaign could have ended much differently as the marines were still largely issued 1903s. in this situation the japs had few machineguns and no SMGs while the US had plenty of both, the advantage of firepower(mixed with better supply chains) is what turned the tide in the south pacific, not tanks, planes and big guns.
Er... after 1943 they had plenty of aircraft support, landed tanks, and battleships
. Don't forget the Navy often pounded an island for days
with naval big guns and aircraft before sending the marines in.