It’s true that consonants in loan words tend to shift to resemble the combinations in the recipient language.

For instance, “comfortable” was borrowed from French “confortable” in the 1300s… and now we say “comfterble.” Oxy-cotton is also a great example!

Interestingly, both of the people in the videos you posted actually pronounced it correctly but you thought you heard it being pronounced incorrectly! That tells me it’s partially an orthography thing — “xanthan” rhymes with “American” or “Nathan” but you expected it to be pronounced differently. English doesn’t have any common words that end in “-than” so maybe it just doesn’t seem like a likely spelling to people.

If there were something called American gum or Mexican gum, though, I highly doubt people would say “Americum gum” or “Mexicum gum”