Here's a link to Portugal's tourism website where they discuss entry requirements:
Measures Implemented in Portugal[Updated on 19 September] To enter in Portugal (including Azores and Madeira), it is no longer required a proof of a negative COVID test or to present a COVID-EU digital certificate or vaccination or recovery certificate issued by third countries, accepted or...
It looks like the US vaccine card is not accepted.
QUOTE:
Mandatory
- A valid
vaccination EU Digital COVID Certificate (with a complete vaccination schedule or with a complete vaccination schedule and a vaccine booster)
- Or a
valid test or
recovery EU Digital COVID Certificate,
- Or a
valid vaccination certificate (with a complete vaccination schedule or a vaccine booster)
or recovery certificate issued by a third country, under reciprocal conditions: Albania, Andorra, Armenia, Benin, Cabo Verde, El Salvador, Faroe Islands, Georgia, Israel, Iceland, Jordan, Lebanon, Liechtenstein, Moldova, Monaco, Montenegro, Morocco, New Zealand, North Macedonia, Norway, Panama, San Marino, Serbia, Singapore, Switzerland, Taiwan, Thailand, Tunisia, Togo, Turkey, Ukraine, United Arab Emirates, United Kingdom and the Crown Dependencies (Jersey, Guernsey and the Isle of Man), Uruguay, The Vatican (
https://ec.europa.eu/info/live-work...nes-europeans/eu-digital-covid-certificate_en),
UNQUOTE