Looks like it was a false alarm, all is normal again at
{http,ftp}.us.debian.org. Is ftp.us.debian.org the master node?
> Same problem now also at {http,ftp}.us.debian.org?
>
> W: Failed to fetch
> bzip2:/var/lib/apt/lists/partial/ftp.us.debian.org_debian_dists_unstable_main_binary-i386_Packages Hash Sum mismatch
> ...