I used to work in Web preservation and we often discussed/collaborated with internet archive.

I was working in a French government-funded Web preservation project.

Many countries have such government-led projects (france, norway, iceland, italy, usa - via the library of congress, slovenia). For a full list of who does that, see https://netpreserve.org/

Short answer: partial replication of the data at other institutions + overlap of the archive at other institutions

Many projects like internet archive exist, they are not necessarily publicly accessible via the internet (in France the archive can be consulted from public libraries via dedicated computers).

If you are interested in the topic, also take a look at the LOCKSS project from Stanford: https://www.lockss.org/