This particular problem, of matching misspelled immigrant surnames was the reason for development of phonetic matching algorithms. See https://stevemorse.org/phonetics/bmpm2.htm
Western slavic languages still use a version of the 'Close unrounded central vowel' implicitly in pronounciation, even though it is not represented in writing. An example of this would be words in Romanian (which has a character representation for this sound) that were adopted from slavic languages. E.g. https://en.wiktionary.org/wiki/b%C3%A2rlog#Romanian
> I'm not sure whether Srp is similar. The Serbian-language word for the Serbian language itself is Srpski (српски), but srp is also Slavic for “sickle”...
Native speaker here, these are in fact two different words, since the change that happens in the root of the word 'Srb' that converts it to 'Srp' when the suffix 'ski' is added is called Consonant voicing or originally 'Jednacenje suglasnika po zvucnosti'.