I don't think Congress has the same level of data as the entire internet going back 30 years. It makes sense for Congress to be centralized due to their specific circumstances and responsibilities. And while most don't think about that, I guarantee someone on the backend did.

Archiving the internet is a massive undertaking, and without a massive war chest and paid staff, a decentralized architecture makes to most sense. On the user end, it could be as simple as installing an app, and specifying the amount of local space you want to contribute while the app transparently handles data allocation.

It would would be similar to running a tor or bitcoin node. User provides the resources while the backend handles the dynamics.