For obvious reasons US does have more of a 'uh we bootstrapped from from first principles' approach to political theory, the UK explicitly does not. I would argue that there are good and robust ways to do things in the former sort of a system, possibly ways that are even better than the latter, but I think the US polity has basically been a 250 year struggle to figure that out. I dunno, the US is not doing terribly, there have been some horrible mistakes, but that's to be expected, there are no sinless governments and societies as far as I can tell.