In fairness, the UK government is masterfully good at bureaucracy. Clear directions; spacious, beautifully designed forms that are easy to read, and that you don't need a team of lawyers to fill out. And jaw-droppingly beautify typography. And an implicit understanding that every piece of UK bureaucracy should be easy to navigate for anyone. And their websites reflect that.

The US government, on the other hand ranks close to the very bottom of 1st world nations for forms culture. Forms that are difficult to read, and even more difficult to fill out accurately, often requiring supplementary information from multiple sources. So much so that people are advised to consult a lawyer just to fill out an application for Tax Identification Number! (My personal worst experience with American forms culture).

So I don't think it's entirely fair to compare UK government websites to American government websites. Navigating a bureaucracy that's fundamentally broken is a significantly different kind of problem.

fwiw, I'm Canadian. Canadian forms culture falls somewhere in between. There aren't a lot of forms that are terribly difficult to fill out; it's rare to find a form that requires more than about a dozen pages of supplementary information (all of which comes with the form when you download it). But still not anywhere as easy to use as UK forms are.