And that is because the vast majority of the price of petrol here in the UK is tax (in fact, multiple taxes). Successive UK governments have long used tax policy, on fuel and otherwise, to deter the use of wasteful, highly polluting vehicles. This has arguably been somewhat successful, though it will be a moot point within a generation in any case because eliminating petrol and diesel vehicles entirely is clearly the goal for several good reasons.

Plenty other forms of produce are dirt cheap. You can eat fruits and salad every day and do it cheaper than any other country I've been to, as long as you don't insist on outliers like multi-colored bell peppers in your food.

As for restaurants, technically fast food counts as restaurants. So I'd be surprised if the US wasn't one of the cheapest in the developed world there too. Hard to compare if you want to factor in quality though.