Forgot to reiterate one thing - the number is quite plausible (given 500,000 Italians enlisted as you mention) if you mark the fact that I noted specifically "the US ARMY" as opposed to the more generic "US ARMED FORCES"...
Again, I am deferring to having heard this cited on PBS.
A.A.C.
Well, it doesn't add up even for "Army"... perhaps in one specific theatre, or a unit, or perhaps it's casualties that was listed, but the numbers just can't work the way you stated them.
Hint...Deferring to PBS is not a good means of supporting your argument--it calls into question all of your statements. :-)