Patch for what?
If it is a basic bug fix, gameplay tweak, cheat or something then yeah you usually just find where the code ended up instead and redo what was done in this new location. Sometimes the people doing localisation might have changed things (occasionally the European division and North American divisions of companies do entirely separate work and may or may not squash some bugs along the way) but usually not.
If you mean straight up translation then also possible. Just a normal translation which usually takes quite a bit of time to do as you have to figure out the formats, expand what needs expanding (characters in the font maybe if there are all accents and punctuation not available/used in English) and do it.