My entire post is about exactly how this is not the case, American values are defined in a document[1].
[1]https://www.archives.gov/founding-docs/declaration-transcrip...
Germany had the Paulskirche-, the Bismarck- and the Weymar-Constitution, all of them before that certain Leader elected into power. He got to define who is worthy/unworthy, decide how to read the document his party represents and change the definition of "un-German"
Not at all...that's when the paper matters the most, because the electorate can see that the person in charge is not upholding our values, purely in contrast to the document. The document sets the baseline. Writing things down has value.
The US has had a total of _one_ government and what it means to be American is in the founding document of that government. To be German is to lay claim to a history and cultural lineage that is filled with many different governments and even different states all-together.
The US has distinct regional and cultural identities as well, to be a Texan means something more akin to being German. Texas has a history that extends beyond the US. One can be American and Texan precisely because they are describe a different thing.
To be American is to ascribe to a certain set of ideals and, as far as someone isn't living up to those ideals, they are "anti-American".
As someone who is neither born American nor German, I can tell you that both terms describe a subjective feeling and not objective facts. Moreover, they are terms to create unity/solidarity among those who identify with them and exclude those who don't.
Unlike of course someone born Italian telling you that it's clear for everyone what it means to be anti-Italian: ...don't know, doesn't eat pasta or sthg...? /s