Here it's used as a rhetorical device, "true Americans" is an appeal to our sense of national identity. Be careful identifying fallacies by the superficial qualities they have, pay attention to the context where phrases are used.
The problem is that people have been passing around a cheat sheet of logical fallacies, but using the mental version of a regex to try and match them. This is not a reliable technique for identifying fallacies. Usually, you would want to recognize them by their content, not their form, and it's essential to know the difference between formal and informal fallacies.