In Polish it’s actually “cuda”, without diacritics (same meaning). Regardless, one often ignores diacritics in writing in English/Western context. My last name has “ń”, though all the airlines insist to put “n” there; same with Western European banks. While for some words they maybe ambiguities if you skip the diacritics they are usually resolved by the context. Polish ppl are def used to read a text without diacritics and not surprised by this. (Of course a larger body text is a bit harder/slower to read, but it happens often when text messaging or in a Western context). I don’t know for sure, but I suspect that Serbian is similar.
I think a lot of this is because, especially historically, people outside Czechia etc didn't know how to type Š. It's an effect of English-speaking countries defining global standards for computers, aviation and so on.
Hypothetically, and with a little exaggeration to make the point, if Sweden had somehow had that global influence in the mid-20th century, the American actress "Raquel Welch" might have been stuck with "Rakuel Velch" in her passport, and Swedish people would wonder why she was annoyed by this.
The “international” spelling is actually the English one. E.g. France and Germany respectively use “tch” and “tsch”, which correspond to the pronunciation in their languages.
