Americans in general won't listen long to a foreign accent.

I know this from my nine years producing a weekly national public radio interview program. Some of my best interviews were with Brits, Japanese and Hungarian intellectuals. The audience for these programs seem to have turned off in the first five minutes.
I was surprised at this public response but I find myself doing the same thing. When the speaker is not in personal proximity it is hard to pay attention and there is no social pressure to do it.
Skeptical of my observation? Many of our favorite TV programs come from Canada (Cold Case) or Britain but they must always be re-created with Americans to be successful in America. You may cite the English parlor TV on public television. Don't bother, the audience is no bigger than the number of people getting vegetarian meals on a flight from Missoula to Kansas City.