canada.ca is the Canadian government's equivalent, as far as a web 1.0-style portal/index into many other sites and resources.

Neither the UK or CA versions have "here's an LLM you can make general inquiries to" though; at least for now that appears to be unique to america.gov. Unclear to me why this required a separate domain with all this branding on it vs just being one of those "let our chatbot help you out!!!" popup widgets on the existing usa.gov.