The USCCB says this of altar servers:
Although institution into the ministry of acolyte is reserved to lay men, the diocesan bishop may permit the liturgical functions of the instituted acolyte to be carried out by altar servers, men and women, boys and girls. Such persons may carry out all the functions listed in no. 100 (with the exception of the distribution of Holy Communion) and nos. 187 - 190 and no. 193 of the General Instruction of the Roman Missal.
This is 190 and 193 (boldface mine: PetraG)
190. In the absence of a Deacon, after the Universal Prayer and while the Priest remains at the chair, the acolyte places the corporal, the purificator, the chalice, the pall, and the Missal on the altar. Then, if necessary, the acolyte assists the Priest in receiving the gifts of the people and, if appropriate, brings the bread and wine to the altar and hands them to the Priest. If incense is being used, the acolyte presents the thurible to the Priest and assists him while he incenses the offerings, the cross, and the altar. Then the acolyte incenses the Priest and the people…
193. After the celebration of Mass, the acolyte and other ministers return together with the Deacon and the Priest in procession to the sacristy, in the same manner and in the same order in which they entered.
The altar servers may not distribute Holy Communion. They may be allowed to do other things that an instituted acolyte does, provided that is not distributing Holy Communion, including the things listed in
The USCCB specifically says that altar servers duties specifically include “carry the cross, the processional candles, hold the book for the priest celebrant when he is not at the altar, carry the incense and censer, present the bread, wine, and water to the priest during the preparation of the gifts or assist him when he receives the gifts from the people, wash the hands of the priest, assist the priest celebrant and deacon as necessary (7)” but that they “may not distribute holy communion unless they have been mandated for this function by the bishop.” (10)