Yes, culture is mainly a choice. However, certain cultural behaviours are due to collective behavioural racial karma, which developed over thousands of years and got into the genetics of these races. However, individuals of all races can choose what kind of culture they wish to associate with.
However, adopting a foreign culture you never had any relation to is likely a symptom of you not liking the culture you were born in, perhaps a sign of self-hatred. You also will never really connect with it on a deeper level than those who are genetically tied to the culture will.
Adopting certain philosophies and mannerisms of other cultures into your life is fine however to improve it.
We have rituals from cultures all over the world. The Grand Ritual of Zeus is a great example of that, adopting several Divine names of our God from numerous cultures. We also use European Runes with Sumerian origins as well as Sanskrit.
The Pagan Gentile cultures have their differences, but we are all ultimately related and connected as children of Zeus. True diversity is maintaining these cultures and appreciating them.