I would recommend you don't read into location data too much.
The way this works is fairly simple. When you get an IP address range assigned, the RIR you get it from, for America in this case, ARIN, allows you to specify the country and geolocation coordinate data to each address block. How accurate of location data you put on your blocks is up to you, you can be quite vague if you wish.
Different "IP Lookup databases" on the internet then index this information and try to make more accurate guesses based on other data they have, such as where the company that owns a specific block is registered, and "augment" the data this way. In many cases this is inaccurate.
If namemc recently switched or updated where they get the information from, this might have been the cause of the change you see. Currently, I do not know which service they use for it.
To give you a more precise answer, the US servers we have are located near the center of Buffalo, NY. I can tell you this with confidence, as I have been in the data halls where the servers are. :)