More nit-picking: Punjab is a place name, not a personal name. It’s a region that was partitioned between India and Pakistan in 1948, and now lies partly in each country.
Your American friend is so young, she thinks Pakistan and India are different places. Which wasn’t the case when the English were first introduced to “Indian” food. And of course, a lot of English Pakistanis came from what’s now ‘India’ anyway, after being displaced during the partition.
Yeah, that’s my guess. In most European languages off the top of my head, the “u” is an “oo” sound. Or /u/ for the IPA folk. So when a foreign word is seen, that’s the instinctual first guess. Similarly, the “a,” gets moved to an “ah” sound, as that’s the typical pronunciation for that letter across many European languages, and not the /ae/ of “cat.” Hence, poon-job. The “pun-jab” pronunciation mentioned before surprises me—I have never heard that. It’s either “poon-job” or “pun-job” as I’ve always heard American speakers say it.
I’m sure that’s true. My friend’s father was born just after the partition, and emigrated to the US in the late 60s. So for their entire lives Pakistan existed as a separate political entity, at least.