does the character depend on the birthplace?
In my opinion it depends on the genes and the cultural environment.I guess that polish women in the US are different from average american women although they live in the same environment.
doesn't it depend on the upbringing?
It is the catholic upbringing.In orthodox countries for example if we do sth that a person does not like or we harm a person,we try to compensate by offering sth to the person like presents whatever.Then the person is grateful.Catholics do not have this mind frame.(protestants just keep punishment).
So if you do sth for a polish girl,it is likely that she will not express gratefullness while a russian girl will be affectionate.It does not mean that the polish girl is not grateful,she does not express that due to upbringing.
no, we are aliens...
No really,I find very few differences between polish and czech girls,maybe polish are more passive and czech are more ''zieckig'' but the feeling is the same.