There are a lot of issues to cover in your first paragraph.
So then say an Autocephalous American Catholic Church was set up,
First of all, personally, I don’t believe the idea of autocephaly as understood today by the Orthodox (both Eastern and Oriental) is patristic. I believe the only truly autocephalous Church is the Catholic Church herself. All other Churches (Western, Eastern, Oriental) are Local Autonomous Churches in relation to the one Catholic Church of Christ. This is proven by the fact that all Churches must submit to the authority of an Ecumenical Council, so it is illogical to claim that in any of the Churches today that are called “autocephalous,” there is no higher authority on earth than the head bishop of that “autocephalous” Church. Further, if the primordial Church truly believed in the concept of several autocephalous authorities, over which there is no greater authority (as it is understood in Orthodoxy
today), then the principle that Rome is the court of final appeal for ALL bishops would never have found any kind of support in the early Church. It is illogical to claim that Patriarchal See A is autocephalous, while simultaneously admitting that one of its bishops can appeal beyond the Patriarchal authority to the See of Rome as court of final appeal. This is especially relevant for me as a Copt, because the Council that affirmed that Rome was the court of final appeal had the approval of one of our greatest Patriarchs in history, Pope St. Athanasius. Pope St. Cyril was true to this patristic Tradition when he wrote to Pope St. Celestine during the Nestorian controversy:
“
We have not confidently abstained from communion with [Nestorius] before informing you of this. Condescend, therefore, to unfold your judgment that we may clearly know whether we ought to communicate with him who cherishes such erroneous doctrine.”
I suppose that in a united Church, local Churches can still call themselves “autocephalous,” but it should be recognized that Rome is the Court of final appeal for a bishop even beyond the decision of a patriarchal synod. In other words, Eastern Churches should simply adhere to the Tradition of the Church in the first millenium.
NOTE: I’m not questioning the notion of “patriarchate”; only the notion of multiple autocephalous Churches.
would they appeal first to Rome or to Constantinople? What about Russia, who should they appeal to?
It’s not “either/or” as far as Rome is concerned, because ancient Tradition establishes that Rome is the final court of appeal for the ENTIRE Church. The canonical procedure, of course, is that a bishop, though he has the prerogative of appealing to Rome, does not have the prerogative to bypass his own local judicial process and go directly to Rome.
As far as the hierarchy of the appeal process, I believe each Apostolic See (i.e. one of the original Pentarchy) is an autonomous entity. Constantinople gained appellate authority over the other Eastern Apostolic Sees only because of the secular authority. As that secular authority no longer exists today, in a united Church, bishops in the Sees of Alexandria, Antioch and Jerusalem, if they wish to appeal beyond their Patriarchate should appeal directly to Rome, not through Constantinople. Bishops from all the non-Apostolic Patriarchal Sees should appeal first to their Mother Church, and then on to Rome (if necessary). The EP will have to work out the jurisdictional issues with the MP, but on principle, the EP is higher in appellate authority than the MP because the MP is not an Apostolic See.
So who would be regarded as the mother Church of an American Patriarchal Church? Thinking about it gives me a headache.

In truth, I don’t believe that in any of the countries outside the Old World, Patriarchal Churches would be feasible and fair for the Eastern/Oriental Churches, because the Latins will always be the majority. I believe the best we should hope for as a united Church in the “New World” are territorial Metropolitan Churches. In areas where a certain Tradition dominates, each local Metropolitan Church will establish its own canons for the proper care of the minority Tradition.
OR
We can live by the principle of personal jurisdiction within territorial jurisdiction where a local Church of a certain Tradition in the territorial jurisdiction of another Tradition is under the direct omophor of a foreign head bishop, but the bishop of that local Church must work in the Synodal context of the territorial jurisdiction.
What are the divides of “East” and “West”?
It would be according to theological Tradition. Don’t forget the Orientals, and the Church of the East.
Is your church still interested in the establishment of Local Churches? If not why not? If so why has it not been done?
Each bishop is the head of a true Church, and the Catholic Church has continuously established new Churches as the need arises, so I’m not sure I understand you. Are you talking about Patriarchates? Can you please clarify your question?
Blessings,
Marduk