The arXiv is where we keep papers on math, physics, etc. It's run by Cornell University.
It seems unlikely that the US government would demand that Cornell destroy the arXiv. But the many copies of the arXiv around the world were shut down on September 15, 2024, and it seems that now all the data resides in the US.
If anyone wants to back up the arXiv, they should go here:
https://info.arxiv.org/help/bulk_data_s3.html
The complete arXiv was 2.7 terabytes in March 2023, and growing at about 100 gigabytes a month.
Also read this, if you want to keep your backup up to date: