Went through Immigration at ATL two weeks ago from AMS with a Latvian Embassy issued US passport -- much different from the ones they issue now. This one has the numbers perforated throughout the passport.
Going through immigration was a breeze. I actually went to the "others" line because it was shorter. Cleared within 10 minutes with a comment of "have a nice day."
Then my luggage was lost on Delta and I didn't have a nice day until two days later.