Sixts False Damage Claim on my German Rental

About a year ago, I rented a car from Sixt in Germany for just two days. To be cautious, I even opted for their mid-level insurance, which carried a $1,000 deductible. Before returning the car, I carefully photographed it from every angle to document that it was in perfect condition. When I dropped it off, no attendant was present to accept the return. Days later, Sixt claimed the vehicle had a deep scratch "down to the primer" and began pursuing me for damages. From the very beginning, I disputed their claim, immediately sending them the photos I had taken at the time of return—clear proof the car was undamaged. Despite this, they ignored my evidence, insisting I was responsible. Eventually they passed me off to a German collection agency, then just a few weeks ago(a full year later), I’m suddenly being contacted by a U.S. collections agency over this supposed damage. Over the past year, I’ve done extensive research—scouring Reddit threads, Facebook groups, and YouTube—and discovered countless stories from others who have faced nearly identical "damage claims" after renting from Sixt and similar companies. It’s a pattern that looks less like legitimate billing and more like a systematic scam. I didn’t cause this damage. I have photographic proof that no such damage existed when I returned the vehicle. Beyond that, this rental took place in Germany—so the idea that a U.S. collections agency or U.S. courts would have any valid jurisdiction here seems far-fetched at best. All I know is that I'm starting the process of contacting my lawyer, my state attorney, filing a formal complaint with the Consumer Financial Protection Bureau(CFPB), Better Business Bureau(BBB), and anywhere else that I can tell my story.