That was actually how things were going to go in the immediate aftermath of the American Revolution - despite religious pluralism and all that, Methodism was the fastest growing denomination even in Colonial America. (Hence part of the reason the Protestant Episcopal Church, as it was then called - to differentiate from the Methodist Episcopal Church (hence the AME and AMEZ churches) - was formed as a survival mechanism for Anglican congregations in the US who did not want to go that way, by way of the Scottish Episcopal Church and its peculiar views as a result of the Jacobite Wars.) It's perfectly conceivable to have Methodism not only be the majority denomination in that case, but even as a de facto state church from the beginning of the Revolution, in that case - with very little alteration to OTL.