I noticed that abroad too that no one batted an eye at using a credit card for tiny transactions worth ~$2, but in the US an independent merchant would either have a $10 minimum or charge a ¢50 fee or both.

I dunno, I'm skeptical that if merchants actually saved more money now they'd pass along those benefits to consumers. Maybe if we were at the beginning of the adoption of cards, but with those costs baked in I'd bet it'd just be pocketed as profit.