The US doesn’t have any required certifications for boat chartering or ownership (yet), but the EU does, the International Proficiency Certificate. According to the US Sailing
press release US charters in the EU were denied the right to charter or required to hire a skipper. I’m pretty sure with a good log book they’d let you charter or require a short check out sail with one of their skippers. Either way, its nice to get more value of your US Sailing certification.