Much of what needs to be said regarding the cultural impact of the Internet is implicit in what has already been written about language and the media.
Just because the Internet already uses electronic representations of linguistic and non-linguistic content (before laboriously turning it back into words and pictures) it will be the leader in the use of new forms of representation of human cultural products; and just because the Internet was from the beginning global, it will most always be the first place that globalized cultural expression will show itself.
However, at least until non-linguistic communication becomes a reality, the Internet is as bound as any other medium by national languages.
Other than in the use of language, the Internet is already in the vanguard of the globalization of sport, education, the law, business, the arts, ethics, life-style, etc etc. But, importantly, as remarked before, the Internet allows and encourages minority interests and groups just as much or even more than it encourages 'global' cultural expression.
Just one, slightly macabre example, to illustrate this. When checking on the 'groupishness' of the Internet, that is, making sure that it does encourage the expression of the human tendency to affiliate, a search was done on the word 'rus' as in toysRus and so on. Immediately up came stumps 'R us and, no, it's not a cricketing group, it's amputees!!