Disappointing to find a "no true Scotsman" fallacy as the top comment.
No true Scotsman is an informal fallacy, an ad hoc attempt to retain an unreasoned assertion. When faced with a counterexample to a universal claim ("no Scotsman would do such a thing"), rather than denying the counterexample or rejecting the original claim, this fallacy modifies the subject of the assertion to exclude the specific case or others like it by rhetoric, without reference to any specific objective rule ("no true Scotsman would do such a thing"; i.e., those who perform that action are not part of our group and thus criticism of that action is not criticism of the group).
If it were an example of the mentioned fallacy, the poster would have to imply that the USA is not to be considered truly civilized. But this is not what the comment says.
I get what you're saying. You're saying the poster isn't implying that the US is not civilized, but rather that given that it is civilized, it should know better.
It still amounts to the same thing. I think you're saying it's not a "no true Scotsman" because instead of a "no true Scotsman would" it's "no true Scotsman should"? But the essence of the fallacy is that it, without argument, applies an attribute (in this case, "no death penalty") to a word ("civilized") and argues based on that unargued assertion that it isn't, or isn't acting like, that word (a Scotsman, or civilized).
Edit: I'll put it this way. Here's the OP: "How can a society which calls itself "civilized" do X?" Similar to "How can a man call himself a Scotsman if he does X?". It's implying, without argument, that X is un-Scotsman-like. It's still the "no true Scotsman" fallacy, with a different sentence structure.