What language has to do with your origin?
Everything. Language and customs are a part of a person's heritage and culture. For example: my daughter's best friend is a Polish born Vietnamese girl. She speaks perfect Polish- her family has assimilated, they own a business, pay taxes and contribute to society. However- she will never be considered Polish because of her obvious physical differences- she has Polish citizenship but she is not Polish.
Polonia in the west are just that- Polonia. They usually don't follow Polish traditions and customs completely but merge them with western culture.
An American born Polonia who speaks bad Polish and has a primary western culture is Polonia. Do not mix culture with ethnicity and citizenship. If a person born in the u.s. from Polish immigrant parents does not speak the language and does not practice the culture- is not culturally Polish. Their ethnicity is Slavic, their culture is American with Polish heritage- they are not Polish.
I speak Polish but I am not Polish- nor will I ever be. Even when I get my Polish citizenship I still will not be Polish.
My kids are half Polish half Canadian. They speak two languages and we have merged two cultures equally. They speak with no noticeable accent in either language- they are completely half and half--but we are not the norm.
Living in the west, going to Polish church and taking Polish language classes in the church basement on the weekends still only gets you the title Polonia- which is different.