Why are Catholic bishops styled as archbishops?

In the British Isles, bishops of both the Roman Catholic Church and the Anglican Churches are all styled "Right Reverend"; archbishops are "Most Reverend": > The Rt Revd John Smith, Bishop of Salisbury > The Most Revd Martin Jones, Archbishop of Liverpool However, in other countries, Roman Catholic bishops are Most Reverend, even where the a Church in the Anglican Communion has a fairly substantial presence (like the United States). In the United States, bishops and archbishops of The Episcopal Church [Anglican] follow the British model, whereas Roman Catholic archbishops **and bishops** are all "Most Reverend". How is that difference (between the custom in the British Isles and that in other Bishops' Conferences) explained? I *guess* that the similarity between the Churches within the British Isles is a hangover from the Reformation, and it would appear to indicate that the distinction existed in the pre-Reformation Church and was carried into the Church of England. In which case, why is there no difference between Catholic bishops and archbishops outside Britain now? When were bishops elevated to archbishops' style? Or, did the nascent Church of England separate the styles (so the Roman styles outside Britain are historic) and then the emancipated Catholic Church simply fall into line when the hierarchy was re-established in the United Kingdom? I don't know where to look for an accurate telling of the history. --- (I'm British. The question is occasioned by finding an American bishop styled as "Most Reverend" and thinking "But he's not an archbishop!")