For me it is USF because of squishy armor and lots of abilities (vehicle crew, smoke barrage, HVAP, switching shell types, etc).
But IMO hardest to play =/= highest micro requirement.
you forgot about usf paper armor late game vs heavy nazi tanks
while the german player is "controlling""microing" his mgs to stand still and his tanks to stand with there
front armor
one clicking with his LMG greens on ur rifleman [a lot of micro going on for the wehrmacht army
]
you are trying to break through
with all your force to flank his tanks and now you can insert the "ability micro"
your rifleman lose while they are tring to come close at long range to one click greensLMG wipe + wehrmacht HMGS
your ATGS bounse every shoot, ur tanks made of paper ...