Are American car parks so ill designed that they're aren't wide enough to allow two cars to pass?
As a Canadian, the answer to the above is yes, a lot of US parking lots are dreadfully designed. They have single, one-way aisles and it is impossible to pass anyone who is sitting in the aisle.
Not really, but it depends. Some parking lots have the angled spots which have one-way aisles that are about as wide a lane on a road. Not enough room for a car to pass one standing.
Parking lots with 90-degree angled parking slots have aisles that are two-way but usually it's a very narrow two-lane (about what you'd get on a road in a suburban area) not allowing for too much passing or movement in traffic flow. This is probably done to maximize space, the narrower the aisles the more cars the parking lot can accommodate or the smaller the parking lot needs to be to allowing space for other shops and/or landscaping.
There's also a hitch... Drivers are... Well, drivers are stupid.
Parking lots don't have lane-lines and such in them which usually translates to drivers in them doing whatever the hell they want. As stated the aisles for standard parking configuration isn't much wider than a regular two-lane road in a low-volume neighborhood. Just enough room for one car to go in each direction with some space to spare. But with no lane-lines people don't usually completely stay to one extreme side or the other and, rather, tend to go down the middle of the aisle which effectively makes a normally 2-way aisle now a one-way aisle. If cars stayed to one extreme side there'd be some decent room to overtake a waiting car. (Though passing is usually discouraged in parking lots as it's an unexpected thing that may make for an accident as a car backing out may wreck into an overtaking car being in the "open" lane.)
Then we get into *how* people back out of the space. I was always taught that when you back out of a space you pull into the nearest lane and orient yourself to be in that lane properly. (i.e. pull out, turning your car to the right so that when you go in "Drive" again you're in the right-lane facing the correct direction.)
Turning your wheel through the backing out-process properly while backing out should allow for the parked-car to do this and still allow for the far lane to continue through the aisle safely. (The inside lane having to hold-up for the backing-out car.)
People don't do this.
Instead they back-out and likely set themselves up to go in the "direction they need to go" rather than the inside lane. This ties up movement in BOTH lanes of the parking aisle.
Then there's the people who don't know what that big wheel in front of them is for. So assuming the "direction they want to go" means pulling into the correct lane they may STILL tie-up both lanes of the aisle as they effectively back straight out of the stall, maybe with a slight slant, put the car into "Drive" and THEN they straighten the car out as they pull forward into the aisle and make a turn. As opposed to turning the car while backing out to stay as much in their lane as is possible.
Granted doing a lot of this may be hard to do as people drive larger and larger cars (read: SUVs) that aren't as maneuverable or easy to see out of when backing out of a space. Or people who drive smaller cars who are flanked by larger cars making see out of the space harder when backing out.
It's all a mess but boils down to people being idiots when they get into their cars and bigger idiots when they get into parking lots that are narrower than most roads and nifty little lines painted on the ground to tell people where they should and shouldn't be.
