Debit cards exist and are very common in the US, more common than credit cards. They also largely use the Visa and Mastercard interchange networks though, but they are also tied directly to your bank account. So I am not sure if I am understanding your comment correctly.
In the US you basically always get a debit card with a bank account but not everyone gets a credit card, either because they are wary of credit or can't get a decent one.
US consumers have credit cards on top of debit cards because they really, really want access to credit. Even overdrafting is really common and a desirable feature for a large chunk of the US population.
You seemingly know much more about the backend than me, so I am still a little confused by your comment, about Interac, for example. The US system allows for consumer-to-merchant debit payments no problem, whatever fees there are are totally invisible to consumers. (I think it's lower than the credit interchange fee?) I can also transfer my money from bank to bank without fees, although sometimes it takes a couple days. Where it really falls down is peer-to-peer instantaneous transfers. There are different things becoming popular but I don't think any of them are particularly good, and reversibility is really important in the US market and systems like Zelle don't seem to appreciate that.