Concerning the Rite of Christian Initiation of Adults Why do the American and Canadian Rites of Initiation differ in numbering and in the way that the rites are sometimes celebrated?
The Canadian and American Rites of Christian Initiation differ because it is basically permitted by Rome.


  ADAPTATIONS BY THE CONFERENCES OF BISHOPS IN THE USE OF THE ROMAN RITUAL
  
  
  In addition to the adaptations envisioned in Christian Initiation, General Introduction (nos.30-33), the rite of Christian initiation of adults allows for other adaptations that will be decided by the conference of bishops.
  Each conference of bishops has discretionary power to make the following decisions:
  to establish for the precatechumenate, where it seems advisable, some way of receiving inquirers who are interested in the catechumenate (see no. 39);
  to insert into the rite of acceptance into the order of catechumens a first exorcism
  and a renunciation of false worship, in regions where paganism is widespread (see nos.
  69-72);
  to decide that in the same rite the tracing of the sign of the cross upon the forehead (nos. 54-55) be replaced by making that sign in front of the forehead, in regions where the act of touching may not seem proper;
  to decide that in the same rite candidates receive a new name in regions where it is the practice of non-Christian religions to give a new name to initiates immediately (no. 73);
  to allow within the same rite, according to local customs, additional rites that symbolize reception into the community (no. 74);
  to establish during the period of the catechumenate, in addition to the usual rites
  (nos. 81-97), ‘rites of passage’: for example, early celebration of the presentations (nos. 144-150, 165-171), the ephphetha rite (nos. 184-186), the catechumens’ recitation of the Creed (nos. 180-183), or even an anointing of the catechumens (nos. 98-102);
  to decide on the omission of the anointing with the oil of catechumens (no. 218) or
  its transferral to the preparation rites for Holy Saturday (nos. 190-194) or its use during
  the period of the catechumen ate as a kind of ‘rite of passage’ (nos. 98-100);
  to make more specific and detailed the formularies of renunciation for the rite of acceptance into the order of catechumens (nos. 70-72) and for the celebration of baptism (no. 217).
  
  
  Rite of Christian Initiation of Adults


Individuals bishops are also allowed to make further adaptions if deemed fitting.

Further insight can be obtained in this Vatican document: INTERNATIONAL COUNCIL FOR CATECHESIS ADULT CATECHESIS IN THE CHRISTIAN COMMUNITY SOME PRINCIPLES AND GUIDELINES.