I need to find a US based repository
DNS resolves archive.ubuntu.com and us.archive.ubuntu.com to IP addresses registered through RIPE as being in the UK. Am I misunderstanding the "us" country code in this case?
Can someone tell me how to assure that what I download from an Ubuntu repo actually came from servers located in the US?
Use https://launchpad.net/ubuntu/+archivemirrors to locate a mirror based in the nation you wish.
Then test the corresponding IP address to confirm that it is in the nation’s assigned range.