Something I really appreciate in Taiwan is a single card works for all transit. What I found cool in Sydney was metro turnstiles would read contactless credit cards. And I'm shocked and thrilled that the Bay Area consolidated on one system.

The US is pretty split up and doesn't use trains outside the NE corridor, so it's not as useful, but it'd be nice if congress would start work on unifying transit payments across the country over the next decade. Also unifying car toll payments. These balkanized systems are just silly.