Eve is the person with the USA accent. Born in England and moved to Connecticut, then back to England. The actress Sandra Oh.
The girl with the 'faux sexy Eastern European spy-girl accent' is the assassin Villanelle. Born in Russia, she speaks many languages, but doesn't like to speak Russian. The whole point of Villanelle is that her life now is a performance. The actress who plays her, Jodie Comer, has a gorgeous scouse accent in real life.