The impact of language on culture is called the Sapir–Whorf hypothesis, and posits that language is a method of unconsciously reflecting social and cultural norms to the point that speaking and living in a specific language affects both worldview and societal mores. The most obvious example of this is the gender-specificity of many languages; while English generally holds to gender-neutral nouns, many languages -- Spanish, Hebrew, Italian -- have different versions of words reflecting the "gender of the topic." This is a difficult concept for English-speakers, but entirely integral to other languages to the point where a Hebrew-speaker will find it odd that English does not have gendered nouns.
Similarly, in a region of any given country where the language is "coarse" or unrefined, we expect to find the culture there also unrefined. The British elite in the 17- and 1800s were very contemptuous of the working class, who did not rise to their level of language; see for example Pygmalion (My Fair Lady), which is not in itself an indictment of unrefined language, but does contain much regarding the gap between "levels" of the same language: Eliza Doolittle's character only changes as her mastery of proper English changes; her former street friends do not change, as their language remains unrefined.
The Sapir–Whorf hypothesis has been criticized and reformulated several times, but remains an interesting topic and has not been definitively disproven.
Not quite. It most definitely affects culture, but it is not the sole factor of culture.