I think you need a RN/RNM to open a bank account even with online banks - I haven’t tried all of them of course so there might be some that work with cpf only

For comparison, one does not need need to get US tax ID number to use a Visa card.

Calling a CPF a "tax ID" is a bit misleading, much like calling an SSN "the way you get social security benefits". You can (even as a non-citizen) get one in a couple mins at the post office, and it's used for literally everything, including things like buying a SIM card or registering for some public WiFi hotspots.

Okay, that's quite a bit less bureaucratic than American EIN, ITIN, or SSN (collectively known as TINs).

How many digits/letters long is it? One problem with American TINs is the entire space is only a billion digits, so it's not possible to assign one to every person in the world. If we could add two more digits or make 3 alphanumeric, it would be a lot more feasible to do this, but that is basically impossible at this point.

> How many digits/letters long is it

nnn.nnn.nnn-nn

A CPF is nationally unique.

You also have a RG/RNE which is unique per state. Not too often you get asked for this one though.