Oracle Team USA matched Emirates Team New Zealand on eight points out of 10 by winning the race and, with a superior finish in a previous event and a race in hand, they are guaranteed top spot on the leaderboard.
"I think the point could end up being incredibly important", said Spithill, who forced Team New Zealand skipper Peter Burling into a penalty at the start and won by 29 seconds in a rematch between the teams that sailed the epic 2013 America's Cup match.
Team NZ will take on the British Ben Ainslie Racing syndicate in this week's Louis Vuitton America's Cup challenger playoffs.
Artemis also led wire-to-wire in their 18 second victory over Team Japan.
The American-backed crew, which includes Australians Spithill and Slingsby, will now train on its own while the challengers sail their semifinals, which start Sunday, and finals.
Emirates Team New Zealand yesterday snared the top challenger ranking with convincing wins over Dean Barker's Softbank Team Japan and French team Groupama, but must now consider who they prefer to meet at the next stage.
Sir Ben Ainslie and Land Rover BAR sailed smoothly throughout the race but, having fallen behind their opponents at the start, the British team could never quite close the gap as the race progressed.
"We made some little errors and then learned a lot and we stayed out for a while afterwards to practice a few things that went wrong during the race and we are really happy with the few improvements we made afterwards".
The holders now have to sit on the sidelines until June 17 when they will defend the cup against one of the challengers.
Radio Sport has live commentary of all Team New Zealand races.
The pre-race pressure was high with the victor of the monumental clash not only taking the bragging rights, but also importantly topping the final Louis Vuitton America's Cup Qualifiers table which means taking a vital point into the showpiece America's Cup Match. presented by Louis Vuitton. If Oracle beats the Kiwis, it would clinch the bonus point on a tiebreaker based on standings in the America's Cup World Series the last two years. The Kiwis reached match point at 8-1 and was way ahead in what would have been the deciding race, but it was abandoned after the time limit expired on a fluky day on San Francisco Bay.
"It's a big one tomorrow", Team USA skipper Jimmy Spithill said.
Team Japan has three points and Team France, two.
Oracle has a second race Saturday, against Land Rover BAR.
Team USA remained stuck on seven points as they were handed just their second defeat of the competition by Artemis Racing of Sweden.