#2 - Williams (9)
You'd never guess if you looked at their most recent season, but Williams are the second-most successful team in terms of constructor's championships. They've only won 7 driver's titles, but they've won two more constructor's as they've often had the best car but not the best driver.
1986 is a key example of this, as Alain Prost in a far worse car won the driver's championship, despite Nigel Mansell and Nelson Piquet comfortably won the Grove outfit the constructor's title. Alan Jones won their first in 1980, just their third year as a constructor! From there, Piquet, Mansell, Prost, Damon Hill and Jacques Villeneuve also won driver's titles at the team, the mid-80's to mid-90's being Williams' golden years.
Their last champion was the only Canadian to win the title, coincidentally, this was also the last champion from the Americas, Frank Williams had a habit of liking South American drivers as well as home-grown British aces. It has been a while, though, 1997 was the last time they won the driver's and constructor's championships and have a long way to climb before they can realistically win another.