JJxvi said:
Your post implies that its easy for a Received Pronunciation speaker to drop their accent back to something more similar to what an American would, and based on the topic of this thread it is very easy to make the inference that youre also saying its harder for an American to go the opposite direction. I dont think there is any difference in the difficulty of Americans to mimic the British or vice versa, and if it does exist its related more to differences in levels of cultural exposure.
In the specific case of global film and television actors, any difference is most likely related to an economic pressure for British, Australian, Irish, South African, New Zealand actors to develop passable American accents in order to have more access to the greatest number of potential roles
*easier
And it is yes. Talk to any acting dialect coach. The first thing they do is have everyone learn to drop their accent to the generic American rhotic. Then they work on learning and building new accents which is harder to perfect.
And Americans for the most part are terrible at British accents - ask any Brit.
But many Brits are so passable without the accent that people are shocked to learn they are Brits.