Has he the right to claim German heritage despite all his knowledge about Germany being nothing Bratwurst and Sauerkraut?
This is unique to German culture but the same could be said of the Germans allowed to gain German citizenship under the Aussiedler laws that enabled Miroslav Klose and Lukas Podolski to join the German nation team. Also there are many areas of the United States that have held onto large amounts of German heritage, including retaining the German language. Not everyone in America is a 1/32nder.
Culture is dynamic.
I agree so what makes a person who grew up in a Wisconsin town founded by German farmers, which has yearly cultural festivals whose grandparents might be named Schmidt, Mueller, Schneider and Kaiser. Less German than a Europhile Berliner whose father was a Turkish immigrant, whose mother was an ardent communist who spent much of her youth in university at Moscow who now works as a financial adviser in London?
Why does the Berliner's ancestor's German experience count as German while the Wisconsin farmer's German experience count for nothing? Because of some arbitrary lines on a map?
My point is that because culture is dynamic no one group holds a monopoly on said culture. It takes centuries for old cultures to transform into new ones. Dutch culture did not exist separate from German culture until the independence and growth in power of the Netherlands. Russian Germans still identified as German (and were recognized as such) for hundreds of years after being invited by Catherine the Great.
Germans in the Americas have only been separated from their European cousins for less than 200 years. This is certainly not long enough to create a new people. For instance the Saxons in England and the Saxons in Germany were not recognized by contemporaries as different peoples until 300 years after colonization. Despite the former being Christian converts and adopting different societies.
Hell, Germany of 300 years ago constituted something different than Germany today.
Does that mean the residents of the German states 300 years ago weren't German?