Betel nut chewing is still found lots of places in South and Southeast Asia.

Not to that extent: it's against regulations in most cities from Singapore (obviously) to Saigon, and it's considered 'old people thing' in general. In Papua you see people with red teeth all the time, blood like stains on sidewalks accompanied by tiny zipper bags, which are very intriguing when you're out of context. I saw a mother giving betel to her 10 yo daughter on a boat ride - It is a bit calming, so...

The streets are littered with beetlenut in Shenzhen, especially Huaqiangbei. Also Chunking Mansion, HK (take the stairs). Would not recommend if you have elevated blood pressure.

It is very pervasive in certain parts of India. Google Pan Masala India.