"FIFA told us they gave him a four-match ban rather than a five-match ban because they appreciated the letter De Rossi wrote them apologising for his actions," said the Italian Football Federation's media spokesman Antonello Valentini.
The four-game suspension included Thursday's final Group E match against Czech Republic, meaning De Rossi would be available for the final if Italy get that far in the tournament.
The Italians face Australia in the last 16 on Monday.
Italy and the U.S. slugged out a bruising 1-1 draw in a controversial encounter last Saturday.
De Rossi was dismissed in the 28th minute for a blatant elbow on McBride right in front of Uruguayan referee Jorge Larrionda.
The American was left with blood all over his face and needed three stitches under his left eye.
A World Cup record-equalling three red cards were shown in the match as the U.S. finished with nine men and Italy with 10.
Italy said they would not appeal against the decision to ban De Rossi for four matches.
Giancarlo Abete, head of Italy's World Cup delegation, said: "If you make a mistake it is right that you pay.
"FIFA's decision needs to be respected and accepted calmly."
