I think the person you responded to went too far in their argument. I would've said that speakers of the same language can have very different culture, but that (in your example) the English-speaking Mongolian girl wouldn't be part of the same culture that she would if she were a Mongolian-speaking Mongolian girl.
Language doesn't dictate patterns of thought, but it certainly shapes them. A concept that might be easy to formulate in Mongolian may be difficult to formulate in English, and the reverse applies. People naturally use the patterns that the language encourages. With different patterns, different group behaviors tend to emerge, because they're easy to think about.
Simultaneously, the culture shapes the language to fit its needs. Given time and isolation, it will become more and more distinctly different.
What you're talking about is the Sapir-Whorf hypothesis, and it is not certain at all. It's highly contested. Language may have an effect on some cognitive processes (again, contested) but definitely not all.
However, language does reflect the cumulative experience of a culture, whether modern speakers are aware of that experience or not. Here's a good illustration: http://youtu.be/kIzFz9T5rhI
So language can reflect a culture, but it probably doesn't dictate it. In the case of the Mongolian girl, she's unlikely to be a nomad these days, and what separates an English speaking Mongolian from a non-English speaking one is usually wealth. So, someone from a wealthy country is probably more culturally similar to her than they might expect.
Yes, I am. The weak variation of the hypothesis. Coming from a computing background, it's difficult to convince myself that it's the case that the structure of a language (whether artificial or natural) doesn't encourage or discourage specific ways to represent meaning.
If the Mongolian girl lives in Englang and speaks English as a first language (e.g. second generation immigrant), then obviously she is far less different culturally to you than a Mongolian girl that just arrived from Ulan Bator.
Cultures have degrees. Losing the language of your culture means you lose a lot of connection to it (can't anymore follow its arts and letters for one, or even casual conversations between people from that culture).
And after a few generations in a different country you're mostly a token X (where X your original culture), except if you (and your family) went to great pains to maintain the connection (the default is losing it).
>Didn't you already explain that there were vastly different subcultures within the population of English language speakers?
Vastly different cultures in arts/consumerism/urban lifestyle/etc, but not vastly different national cultures.
A 3rd-gen British Mongolian can be a spiky haired punk, something totally different from a 3rd-gen British Italian dubstep fan, but they're both hardly major representatives of Mongolian and Italian cultures.
>Don't you think there's more to culture than mutual unintelligibility?
Given that all culture is made into some language or another, and more especially in some national cultural context or another, then, yes, there is something more, but not much.
Language and culture are not linearly independent.
So a young nomadic Mongolian girl and I (UK, middle-age, male, working in craft/retail) don't represent different cultures because we can both speak English?
Go on, explain, clearly I don't understand.
Didn't you already explain that there were vastly different subcultures within the population of English language speakers? Don't you think there's more to culture than mutual unintelligibility?