Germany often makes me wish I could just show them my family history of when we immigrated to the US so they can let me back in.
The exact rules are complicated but it's worth looking in to.
Not saying that Germany shouldn't "let you back in" if you want to immigrate back, but the mere fact that your ancestors were German should not qualify you more (safe for certain exceptional populations in recent war history) than others whose ancestors might for instance come from the UK.
In the eyes of Germany, if you parents were German you are German too, even if your parents never visited Germany.
The chain is only broken if you apply for foreign citizenship or serve in foreign armed forces.
To me it is bizarre that the mere fact of being on holiday in America at your time of birth makes you American.