It was Raikkonen'sa first win in more than five years and 113 races dating back to the 2013 Australian Grand Prix – and his first win for Ferrari since 2009.
The four-time champion German, who kept alive his faint title hopes by finishing fourth behind championship leader Lewis Hamilton of Mercedes, said the team did not understand what was wrong with their upgrades.
Sebastian Vettel said he felt mixed emotions after keeping his slender title challenge alive by finishing fourth in the United States Grand Prix.
Hamilton topped the times with a late flying lap that kept him narrowly ahead of his only remaining title rival Sebastian Vettel.
Vettel says he slowed enough to respect the situation, adding that he felt unhappy at the use of precise delta times.
Hamilton topped the times for Mercedes in the rain-abbreviated second practice at the Circuit of the Americas which only burst into life for the final 40 minutes as the track dried.
Sebastian Vettel recognised on Thursday that he and Ferrari had made mistakes this season but refused to single out the moment where his hopes of winning a fifth Formula One title ended.
Switzerland's ATS news agency said the incident in May occurred when Raikkonen veered to avoid an oncoming vehicle and collided with a car parked to his right.
Hamilton is in the form of his life, hungry for more and as motivated as ever.
Lewis Hamilton wins the Japanese Grand Prix while Sebastian Vettel, the Briton's closest rival, finishes sixth.
Sebastian Vettel refused to blame Ferrari after a wrong tyre choice left him eighth on the grid for Sunday's Japanese Grand Prix.
the reigning world champion, who leads his Ferrari rival by 50 points with five races left this season, survived a close shave in the morning session at Suzuka when he deftly avoided smashing his Mercedes into Pierre Gasly's Toro Rosso.
Vettel also went on the defensive when asked if this week's Suzuka race was make-or-break in terms of his waning hopes of pipping Hamilton to a fifth world title.
Sebastian Vettel must win the Japanese Grand Prix to stay in contention for the Formula One title.
Ferrari is bringing the surprising new Monza SP1 and SP2 roadsters to Paris, inspired by the brand's emblematic barchetta racers, such as the 1948 166MM or the 1954 750 Monza.
Vettel is 40 points adrift of Mercedes rival Lewis Hamilton with six races remaining and is running out of time to reassert himself in the battle of the four times world champions.
Ferrari has been making the limited-edition hybrid LaFerrari for several years, which it has described as offering the most extreme performance ever achieved by one of its production cars.
Ferrari will build fewer than 500 of the two models combined and all have been assigned to eligible clients already.
Sebastian Vettel conceded that his Ferrari was not equipped to win the Singapore Grand Prix.
The German arrived in Singapore 30 points behind Hamilton, with only seven races left to overhaul the Mercedes driver.
The sleek and aggressive cars feature bigger wheels with a more integrated halo head-protection system and simpler front and rear wings.
Haas team principal Guenther Steiner felt it was too early to make a call on the young driver without knowing what his future plans were.
Sebastian Vettel expressed his regret over mistakes that have cost him the lead in the Formula One standings, but also said that he believes he can still overhaul current championship leader Lewis Hamilton.
The flamboyant businessman apparently purchased the luxury car for the reality TV star as a wedding gift.