While I agree that culture can & should drive decisions about content, colors, themes, imagery, etc, I'd argue that from a UX and technical perspective the language has a much greater impact on the outcome.
I work with language learning products (designed primarily for a U.S. English-speaking audience) that generally share a common UI across more than two dozen different languages. Some key issues we encounter regularly:
Right-to-Left text, workflows & layout variations
RTL support can be very difficult to adjust later on if you didn't plan for it initially, or if you lack proper tools & subject knowledge.
- Left-to-right mindset & designs can easily overlook usability issues that emerge when the language & expectations are mirror opposites. Where does "Submit" really belong? What direction does that swipe gesture really need to go in?
- Buttons, inputs, menus, and that pixel-perfect grid alignment you created often need to be reversed. Sometimes the browser/OS is smart enough to handle it for you, sometimes not, or the way your programmers coded the site prevents it from doing so. Oops.
- Just getting properly created content can be a pain: e.g. Arabic text created in U.S. versions of Adobe products is all disjointed & wrong (and your artists probably won't know the difference).
Support for non-Latin typefaces
- Required fonts may not be installed, or may need different encoding that even UTF-8 doesn't cover. Users get the "?" or "boxes with Xs in them".
There are often competing romanization/phonetic standards, and sites may not have the ability to input native language characters where often only Latin ones are expected (urls, names, passwords, addresses, etc).
Many African & Asian languages require custom 3rd party keyboards or input methods, and you can't be sure which one people will use.
Dynamic Type Considerations
There's huge, unpredictable variation between how much space written languages require. A 140-character Tweet is typically vapid, abbrev'd, & curt in English, but can contain significant grammatically correct content in Chinese. This affects UI design by requiring adaptive/flexible layouts, text input areas, menu design/terminology, etc. (Note that in examples below I gave up trying to position the Arabic character count to the right... I couldn't figure out how to put it where I wanted it)!
- English: My hovercraft is full of eels (29)
- Arabic: (حَوّامتي مُمْتِلئة بِأَنْقَلَيْسون (23
- Russian: Моё судно на воздушной подушке полно угрей (42)
- Swahili: Gari langu linaloangama limejaa na mikunga (43)
- Mandarin: 我的氣墊船裝滿了鱔魚 (10)
You keep using that word ... I don't think it means what you think it means...
You're only as good as your bilingual Subject Matter Expert.
If you expect "port" to mean "a dessert wine" but they translate it as "a place for boats to dock" and nobody else involved is able to spot the error, you're going to seriously confuse your users.
While cultural considerations play a significant role in presentation, messaging, expectations, etc, sometimes all that preparation goes out the window due to translation error & simple misunderstanding.
Expectations & Conventions
Popular Japanese news & chat websites today often remain a rainbow of colors, dancing cutesy gifs, tiny/heavy text, and layouts straight out of the late 1990s, but they've also used QR codes & mobile email/browsers for that long, which is unusual. Mobile-savvy, but comfortable with "bad" (from an outside perspective) layout & design. Lots of cultural influence in this case vs language, but there's a definite connection.
Also consider that the internet is still largely English-driven. Even though specs have changed to accommodate non-Latin URLs, etc, many users still must adjust their thinking and behavior to interact in a 2nd language. Conventions (mentioned in the "Chinese Mobile" link above) like name fields, passwords, captchas, login processes & security questions often require the ability to read/write/understand some English, romanize your name/address, etc. Can you imagine if every website made you write in Chinese & it wasn't your native language?