New requirements for US travel to Spain
pain is now following the EU Recommendation and has put it into their national law: As of midnight on Sunday, September 5 (the night from Sunday to Monday Spanish time), the entry requirements for travellers from the United States to Spain will have changed again.
As a traveller with a completed vaccination program, you will be allowed to enter Spain but you will now have to provide proof of vaccination. I presume that you will see this when you open your SpTH application for the Spanish QR code and enter your vaccination details during the 48 hour period before your flight.