I think the main difference is that bikes generally ride closer to the parked cars than cars. But yeah, looking before making any movement on the road seems like a no brainer.
Not really. It's the same - as close as a few finger widths.
To pick a city street at random, look at [1] - a road so quiet you can't see a single moving car in either direction, and it's wide enough you could fit five vehicles abreast.
Americans don't pass within a few finger widths of a parked car, because they can leave a six foot gap just as easily.
[1] https://www.google.co.uk/maps/@37.438309,-122.1449024,3a,75y...