I couldn't find US/Eastern or America/Detroit in the timezone selections for my user profile. Moreover, when setting my country to United States, only a few America/* timezones were visible.
I tried to do the same, but the problem you described didn't hanppen to me. Timezones are taken from the list provided by the pytz library. US/Eastern only appears when you haven't selected any country yet, because it has been deprecated and therefore it is not linked to any country, but it's still in the "general" list for backward compatibility. When I select "United States" as my country I get a list of 30 timezones, including America/Detroit, and they are exactly the same provided by IANA here, so I don't think there's something missing, at least on my installation.
I hope you can give me some additional details so that I can figure out where the bug is and how to fix it.
The root cause appears to be this bug https://bugs.launchpad.net/pytz/+bug/383171 It's only a problem when easy_install is used, and has no fix available. Best for us to change our deployment mechanism to use pip instead of easy_install