A resposta oficial é: tente obter um ESTA.
How is “dual citizen” or “dual national” defined? What if I was born in a country, but never lived there and do not consider myself a national or citizen?
We will make nationality determinations in accordance with U.S. legal standards and practices, not merely by reference to the laws and practices of foreign governments. If an individual believes that he or she is eligible for an ESTA travel authorization, the individual should apply for an ESTA, answer all questions truthfully and accurately, and that individual’s eligibility for an ESTA authorization will be determined in accordance with U.S. law. If you have any questions, please contact CBP at 1-202-344-3710.
E se você não conseguir um ESTA? link
The new VWP eligibility requirements do not bar legitimate travel to the United States. If a traveler is not granted an ESTA, the traveler will need to obtain a U.S. visa from a U.S. Embassy or Consulate.