Then Constantinople, the Church of Greece, Serbia and Romania can join North America back again under the Pope of Rome.
Part of the West, namely North America (at least North of Mexico) is autocephalous.
According to some, not all.
Simply because they disagree with your view of OCA autocephaly?? That seems rather harsh.
No, because their rejection of the OCA's autocephaly undermines their own claims to it as well.
Unlikely the OCA, those churches do have universally-recognised autocephaly.
They do now, except for Rome. Rome didn't agree or recognize the autocephaly of Constantinople until 1214, after it had fallen into schism and heresy, and after it sacked the see and put up its own suffragan on St. John Chrysostom's throne. AFAIK never gave up its claims on the lands that the Iconoclast emperors switched to from Rome to New Rome which now make up the Church of Greece and the Church of Albania, as well as the Patriarchates of Serbia nd Romania. If the OCA's Tomos doesn't bind Rome, there is no reason it would be bound by any of the Tomoi of these Churches as well, except for Constantinople, perhaps:but then its territory is beyond what Constantinople I and Chalcedon defined for it.
The Phanar didn't recognize the autocephaly of Georgia until 1990. Since Georgia had been granted autcephaly in 486 by its Mother Church of Antioch, it didn't hold its breath for Constantinople's approval. As long as canonical communion is not disturbed, it's not a problem.
In any case, union with Rome is by no means certain. Hypothetical or no hypothetical, the cart does not go before the horse.
Cardinal Ratzinger was talking more sensibly when he spoke of the various Episcopal Conferences evolving into autonomous/sui juris churches, but then Pope Benedict XVI abolished the Patriarchate of the West without such a devolution.