Most North Americans (>97%) and those from the U.K., when enumerating to others, count first on their index finger (forefinger), second on their middle finger, then the ring finger, pinkie and finally the thumb. However those from mainland Europe count first on their thumb, second on their forefinger, middle finger, etc. (Pease).
Note: The original video has, since the original post, been removed from its online source. The images below however, were captured from this video.
An emblem is a nonverbal term for a body language signal - the meaning of which is clearly and widely recognized within a city, a region or country and occasionally world-wide. The Thumbs-Up is just such a definitive and widely recognized emblem.
When North Americans and others count first with their forefingers - it carries with it the strong disadvantage of being confused with (both consciously and subconsciously) pointing. Index finger pointing (another emblem) is universally offensive and thus its use should be almost always avoided (there are rare exceptions).
So when President Obama (displayed twice in this short video), or the rest of us count first with the thumb - we "Accentuate the positive and eliminate the negative" (Thank you Johnny Mercer) - something the President, with the recent government shut down, threatened default and Obamacare miscues - is in great need of lately.
Nonverbal Communication Analysis No. 2563: President Obama's Subtle Anger - Body Language of Government Shutdown & the Debt Ceiling
Nonverbal Communication Analysis No. 2561: President Obama's Self-Righteous Jaw Wiggle
Nonverbal Communication Analysis No. 2541: Barack Obama, Permanent U.N. Security Council Members, Syria's Chemical Weapon Disarmament and a Presidential Gaffe - Body Language in the Oval Office
Nonverbal Communication Analysis No. 2511: Barack Obama & Vladimir Putin Handshake at 2013 G20 Meeting
Nonverbal Communication Analysis #2160: Index Finger (Forefinger) Pointing in Politics - The Third (and Final) 2012 Presidential Debates - Body Language of Being an Alpha Male without Offending
Negotiation Body Language Secret # 349: Julia Gillard, Pointing with Two Fingers (or more)
Nonverbal Communication Analysis # 1899: Bill Cassidy and "Obama-care" - Letting your Body Language Detract from your Message
Leadership Secret # 222: Angela Merkel - Palms Down vs. Palms Up
Nonverbal Communication Analysis # 1918: Vladimir Putin - Pointing with Pen Surrogates - Sharp vs. Blunt