Incidentally I tried to use Venmo while in the US, but the app was geo-blocked so I couldn’t install it with a Google Play account set to the UK.
Interestingly, you might actually have that a bit backwards - North America is the only place I know of that doesn't have free (or with a fee of a few cents), near-instant bank transfers. It actually surprised me how backwards the banking system seemed the first time I was in the US (coming from West Africa).
The closest thing we have is Nubank, which is a mobile-only bank, but even that is not nearly as universal as WhatsApp.
Essentially everyone with a phone number uses WhatsApp, but payment apps so far have been restricted mostly to the 20s ~ early 30s audiences in terms of adoption.
Anecdotal evidence, I know, but lacking proper studies...
I don’t have an account, nor have seen somebody using it, though. I’m totally outside their target group.
UPI payments are very popular in India and GooglePay really did a good job in getting the market share here in India.