Walking across a treeless parking lot in Oklahoma in summer would be my idea of hell. Same goes for winter, with weather at the other extreme. I wouldn't fancy schlepping a 40 lb bag of kibble or cat litter back to my car either way. Most of the US has a continental climate and experiences heat, humidity, and cold that you don't get in Britain. The heat in summer comes at you even from the pavement.
A lot of the US has shopping areas that are characterized by big box stores and supermarkets arranged around a big ground level car park (many acres of parking). Many of the supermarkets and other stores have trollies with automatic locks that prevent them being pushed beyond a certain distance from the doors because retrieving them is really difficult. This makes strategic parking in the middle of the car park a risky idea.
It's well nigh impossible to reverse into an angled spot because the angle is in the direction of traffic flow. You'd have to do almost a hairpin reverse. You would have difficulty getting out too, since you'd be facing into oncoming traffic. It's nothing to do with the length of the cars, in other words.
Quick, angled parking makes discernment of your intentions very easy, for both pedestrians and other drivers, making it safer. Your turn signal and brake lights tell the driver behind or any pedestrians that you're pulling over to the right. Activating your turn signal, pulling up past a perpendicular spot, going into reverse - all make it a slower and more difficult process, and you risk some chancer sliding up behind you and driving straight into the spot (which happened quite often when my mum was learning to drive in Dublin). When you're backing in, it's hard to see people getting out of cars in the adjoining spaces too, and they might not see you. Going forward into an angled spot, you can easily brake if someone in an adjacent spot opens a door, and your line of sight when you're reversing out only has to include traffic on your side of the street or aisle.