A Punjabi Sikh can renounce his religion but he would still be Punjabi.

(Sikhism is the dominant religion of the Punjab region.)

Most Punjabis are not Sikhs. If you live in North America, a lot of Punjabis you may have come across may have been Sikhs.

(Nearly) All Sikhs are Punjabi but not all Punjabis are Sikh.

The P in Pakistan (a majority Muslim country) arguably stands for Punjab,

From wikipedia:

> using it as an acronym .., and referring to the names of the five northern regions of the British Raj: Punjab, Afghania, Kashmir, Sindh, and Baluchistan.

That said, there are a non-trivial number of Sikhs in the area, at least one Sikh holy site is very near the Pakistan-India border in the Punjab region.

My family hailed from East Punjab before the Partition and wasn’t (and isn’t) Sikh.

There are many non-Sikh Punjabis.