Apologies I haven't been able to find the answer to this in my search:
For proof of residency, does it matter how old the document is? The latest email from CBP states:
" In addition to your entry document (e.g., your passport), you will need documents providing evidence of residency. Examples are driver's license (if the address is current), mortgage statement, rental payment statement, utility bill, etc
I'm a US citizen resident in Germany. My German license doesn't have my address on it. I'll take a 1-month old notice of my gas bill going up in price and hope for the best. In Germany we also have an official registration of our address (the 'anmeldung') that I can take along too. It's several years old as I haven't moved house