SILVERSTONE, England -- As Formula One expands its reach into the United States, there's still a missing ingredient that could keep some fans away from the stands - an American driver on the grid.

There hasn't been an American in Formula One since 2007 when Scott Speed drove for Toro Rosso. But the pressure is building for an American to make the jump now that the United States successfully hosted the U.S. Grand Prix in Austin, Texas, last year and is set to hold second grand prix in New Jersey as soon as 2014.

"It would be tremendous boost for Formula One to have an American driver," Mario Andretti, the Formula One champion in 1978, told The Associated Press. "It would not only be good for America but also Formula One. No question about it. The U.S. is a very powerful nation from the standpoint of the financial situation. Every company in Formula One now does business in the Unites States."

Scores of Americans have given F1 a try but few have succeeded. Andretti was the last American to win a drivers' championship title and before him it was Phil Hill in 1961. More common were the likes of Andretti's son Michael, who raced 13 grand prix races for McLaren in 1993 with a third-place finish as his best result. Speed never scored a point in the two years he raced in F1.

There was talk in 2010 of creating an American team dubbed USF1 team with strong backing from YouTube co-founder Chad Hurley and featuring Danica Patrick and possibly Speed as drivers. But USF1 struggled to attract sponsors amid the global recession and ran afoul of F1 when it didn't race in 2010.

The dearth of drivers - there are only Americans Alexander Rossi and Conor Daly in all the F1 feeders - is blamed on the a mix of cultural and financial factors. Among the biggest challenges is raising the millions needed to fund a team from American corporations that may have doubts about the benefits of investing in a sport that is not a major attraction in the U.S.

"It's extremely difficult for an American mostly because there is no American support from companies," said Speed, who now races in NASCAR and Global Rally Cross. "Why would an American company spend x amount of money in Formula One when they can get 10 times that exposure in America racing NASCAR? It makes zero sense financially."

F1 drivers and executives said it also can be difficult for an American to make the transition to F1 since they are raised on tracks and a system that grooms them for IndyCar and NASCAR rather than serpentine circuits of Europe. There also isn't the kind of support system that European drivers can count on to provide mentoring and the occasional break as they attempt to rise through the ranks of the sport.

"Formula One has flirted with North American for many years but Formula One hasn't been seen as the pinnacle of the sport in the eyes of youngster in North America. North America has evolved in a slightly different approach with things like NASCAR," said McLaren's Martin Whitmarsh, who heads the F1 teams' association. "North American doesn't have the karting program. Without exception, every single one of these (F1) drivers started at 8 or 9 in karting and went into competitive karting. Karting became the launch pad for their careers."

In the short term, Whitmarsh said prospective American drivers will have to go to Europe early on in their careers. But Andretti said the addition of two American races should help in the long-term - by inspiring more youngsters to take up the sport, providing the facilities needed to develop that talent and convincing American companies to step up their sponsorship.