When you say it works fine
I have two Amazon firestic tv's A Amazon Echo and a Amazon show all linked to my UK amazon account.
All works well (In English) alexa can even do English to Polish translations.
If you wish to have English/American or whatever tv and radio available on firestick and echo, its best to configure them on a separate router which uses a smart vpn to pretend that all the devices are in the uk, us ,etc, I use the smartdns proxy service.
Don't think Alexa is available in Polish yet ,might be wrong