An American-style option permits exercise before expiration, subject to the contract and broker deadlines. A European-style option restricts exercise to expiration. These terms describe exercise rights, not geography.
U.S. listed equity options are generally American-style, while index and futures products can use different styles. Confirm the exact series. Selling an option to close is different from exercising it.
With otherwise identical terms, the additional exercise right cannot reduce theoretical option value. Actual quoted prices may also differ for other reasons.
Content reviewed:
Primary references: OIC exercise guidance; OIC product specifications. Editorial standards.