I think that it is half because of how the US is so spread out and half because of the love affair with the car. I gave up my car years before I left the States, and outside of NYC and a handful of cities east of it, everything is set up with the idea that people drive everywhere.
The fact that public transport is sketchy in a lot of places (sometimes impractical) was used as an excuse I think for people to hold onto their cars. Now that people are getting to the point where they can't afford to run them, there isn't the money to change how the US approaches convenience. What is convenient for people in cars is usually a huge pain in the ass for everyone else, which I am sure more people are starting to see.
When I would use public transport to do grocery shopping in a rust-belt city, unless I went to Aldi or our co-op, I'd have to traverse a massive parking lot with no pavement for pedestrians to walk (in most cases). That's not because putting one in would be impractical. Honestly, it's because businesses didn't want to encourage the type of people who use public transport. Don't think that's true? It was such an issue that a worker commuting home from a local upscale shopping mall was killed crossing the road to get to a bus stop because it was put in such a bad location, and the mall admitted that they had wanted to discourage people who used the bus.
Anyway, I admit at one point I used drive-thrus a lot. If I were ever to get my licence again, I would refuse to use one. I don't blame people wanting them really. I blame people not realising what being so dependent on cars and favouring that sort of business can do to a culture, the environment, etc.
ETA: Not that the UK's perfect when it comes to public transport and not encouraging a sense of entitlement for people driving. The fact that I have to yield to someone turning into my crosswalk (or approaching it for that matter) unless it's a zebra (which I am so afraid to use after seeing so many tear through them) or a green man is ridiculous. We are either seen as a lane of traffic or we become an after thought to the scheme of traffic, which to me is ridiculous.