Studabaker, aged 33, from Michigan, pleaded guilty to child abduction and inciting a child to commit gross indecency at Manchester Crown Court in February.
Mr Justice Leveson sentenced him to four-and-a-half years in jail for each offence to run concurrently.
The court was told the pair had “met” a year earlier on the internet.
Studabaker flew to Paris with the girl after an arranged meeting at Manchester Airport last July.
Prosecutor Beverley Lunt said at an earlier hearing that Studabaker groomed his victim so she would not object to sexual activity when they met up.
On their first night in the Paris hotel, on July 12, they slept in separate beds, but the next day they bought vodka and spent the evening kissing.
She added: “They both woke up later on the Sunday night and there was more kissing and then they had sexual intercourse on her bed.”
The girl, who lives with her family in Greater Manchester and cannot be named for legal reasons, was reported missing at 11pm on July 12, about 15 hours after telling her parents she was going into town with friends.
An international manhunt was launched as the pair went from Paris to Strasbourg and then on to Stuttgart in Germany.
In Stuttgart, on July 15, the girl rang her parents and told them she was safe. She flew back to Britain alone the following day.
Studabaker went to Frankfurt and was arrested outside the US embassy on July 16, before being extradited to Britain.
He confessed to German police he had met the girl on a “cartoony” website called neopets.com.
Greater Manchester Police and the FBI seized four computers to which Studabaker had access and two computers used by the girl.
They found numerous e-mails penned by the former marine. In some he coerced the girl into taking part in “cybersex”.
Prosecutor Ms Lunt said that while the 12-year-old’s messages were romantic and innocent, his described acts of sexual foreplay and sexual intercourse in graphic detail.