Height and mass give a number of advantages. While I do not discount their bravery, Japanese soldiers had a far higher death rate in the pacific campaign than american soldiers. The factors behind this are many: training, arms, logisitics etc.
Battle of Okinawa 2 Japanese dead for each American.
Battle of Guadalcanal: 4.42 Japanese dead for each American
Battle of Saipan: 8.82 Japanese dead for each American
Battle of Iwo Jima: 3.08 Japanese dead for each American
In vietnam its 4.86 NVA/VC dead for each American, though 1.57 if you include all allies.
All things being considered equal, larger men can carry heavier loads, more ammo, heavier weapons, construct fortifications more quickly. Doesn't mean smaller fighters are any less ferocious, but makes things more difficult for logistics.