In the US, former colonists, particularly in port areas such as Boston, which maintained close trading links with England, also adopted RP. From the Southeastern coast, RP spread throughout the South, following the wealth of the plantation owners.
Economic and political elites
After the Civil War and industrialisation, political and economic power passed from the ports and cotton fields to emergent manufacturing centres in the Mid Atlantic and Midwest. Pittsburgh, Cleveland, Chicago and Detroit were in their ascendency and English cultural and linguistic influence began to wane. These new hubs were populated by Scottish and Irish immigrants and other regions of the UK where rhotic English was still spoken widely. The new economic and political elites didn’t speak RP and, as a consequence, it lost its status. What resulted, General American, is now only spoken by a minority of Americans, mostly in the Midwest. Other areas have developed their own distinct variations over time.
Thanks to Matt Soniak