There are no European stations in the so-called extended AM band from 1620 to 1700 kHz. This means even the weak transatlantic signals can be heard without any local interference.
One of the lowest power US stations I have ever heard is WPTX from Lexington Park (MD). I arrived on 1690 kHz at 02:29 UTC and the station faded out soon afterwards – but I was able to record a station identification!