Shannon Boxx and Abby Wambach also scored for the Americans, who are seeking their ninth title in 18 appearances in the event.
Iceland nearly scored first with a header from inside the penalty area in the 19th minute, but goalkeeper Jillian Loyden made the save.
Buehlers opened the scoring off a corner by Lauren Cheney corner in the 48th, and Boxx doubled the lead when she headed in Christie Rampone's cross in the 63rd.
Wambach scored her 154th career goal off an assist by Alex Morgan in the 86th, putting her four goals away from tying Mia Hamm's team record.
More Sports Headlines
Snohomish mixed martial artist returns to her first love Mariners beat Twins 4-3 in 11 innings Charles scores 29 points, Liberty beat Storm 78-62 Park wins Women's British Open, captures 4th different major Perry wins 2nd straight Champions Tour's 3M Championship Merritt shoots 67 to win Quicken Loans National by 3 shots Triple Crown winner American Pharoah wins $1.75 million Haskell Invitational Bills' Ryan names Incognito starting left guard
Our new comment system is not supported in IE 7. Please upgrade your browser here.