I understand crypto can work with micro transactions but it's unclear to me that usd would not work. I know it's expensive through the credit card model but surely some version of mobile could be adopted.
You could use a blockchain to make payments denominated in USD. (e.g. Ripple) Previous to blockchains it was generally thought that micropayment protocols were expensive: after Bitcoin, people stopped caring about what they cost.
Blockchain or not, it is hard to get the costs down. Some of the problems of the credit card model (fraud) never go away.