I see power cables running out to a car parked in front of a house fairly regularly.

In inner Sydney suburbs with terrace houses, the 2sigma distance to your street parked car might be 100 metres. You can't run an extension cord that far

The government/local councils seem to be able to work out how to power the parking meters. There's no reason why each parking spot couldn't have a charging pole installed with smartcard or NFC via mobile app registration and payment.

There are plenty of solutions, what's needed is the will of government to deploy those solutions.

How impractical is assigning parking spots?

> in the US the majority of all cars are not parked in a garage or driveway.

Source? That seems highly unlikely

The US as a whole is 65% homeowners, but population density drives that down. The Bay Area is below 44%. There are hundreds of thousands of apartments here with street parking where you can find it, or rows of carports in 2–3 story complexes that may or may not be lit but definitely no metered outlets.

Yep, I live in the city – most folks in apartments don't have a car. Id still hazard to say that most cars in America live in a garage or driveway and OP didn't back up their claim so :shrug:

Chargers are installed in parking lots everywhere. Just because you haven't noticed them doesn't mean they aren't there.

Charging points installed on lamp posts, due to lamp posts switching to LED lights there's lots of spare power capacity.