Generally, the Entrance Antiphon comes from the Roman Missal. This is the book the priest reads from at the altar.
According to the 2002 General Instruction for the Roman Missal, approved for the U.S.A.
“48. The singing at this time is done either alternately by the choir and the people or in a similar way by the cantor and the people, or entirely by the people, or by the choir alone. In the dioceses of the United States of America there are four options for the Entrance Chant: (1) the antiphon from the Roman Missal or the Psalm from the Roman Gradual as set to music there or in another musical setting; (2) the seasonal antiphon and Psalm of the Simple Gradual; (3) a song from another collection of psalms and antiphons, approved by the Conference of Bishops or the Diocesan Bishop, including psalms arranged in responsorial or metrical forms; (4) a suitable liturgical song similarly approved by the Conference of Bishops or the Diocesan Bishop. [footnote 55: Cf. John Paul II, Apostolic Letter Dies Domini, 31 May 1998 , no. 50: AAS 90 (1998), p. 745.]
If there is no singing at the entrance, the antiphon in the Missal is recited either by the faithful, or by some of them, or by a lector; otherwise, it is recited by the priest himself, who may even adapt it as an introductory explanation (cf. above, no. 31).”
This last sentence allows the priest to modify the Entrance Antiphon.
The Roman Gradual and Simple Gradual are books that have been published in Latin. I am not sure if there are approved translations of these into English. But the Mass (or parts of it) can be done in Latin, so certainly these Latin versions could be used.
