You need an ETA for Cape Verde if you have a United States passport

Travelers need travel authorization to visit Cape Verde for Business or Tourism. The Electronic Travel Authorization (EASE) for Cape Verde is required for visa-exempt visitors entering Cape Verde. It is an online application. If approved, travelers will receive an eTA confirmation electronically. When travelers arrive in Cape Verde, the border crossing will ask for a passport and check electronic records to ensure travelers have the proper visa. An EASE is electronically linked to the passport and valid for up to 1 year. When travelers receive a new passport, they must apply for a new eTA. For all other visas, please visit the government site. Travelers should complete the EASE application online a minimum of 5 days before traveling to Cape Verde. Travelers unable to complete the EASE before arrival can complete the EASE upon arrival, but may be subject to an additional fee. This EASE approval is not required for the following travelers: -Travelers under the age of 2; -Travelers in transit through Cape Verde; -Travelers who are resident foreign nationals upon presentation of a Residence Permit, Residence Visa, or another valid identification document.