Horn6721,
Public disapproval for (and subsequent divisiveness regarding) the Iraq war increased once the claims (by President Bush's administration) regarding imminent threats from Iraqi nuclear, chemical and biological weapons were found to have been false. But point taken regarding the high approval for U.S. action prior to the start of the war.
Maybe the passage of NAFTA or the Vietnam war would have been better examples, my point about divisiveness caused by U.S. Presidents was meant to be generic (i.e. divisiveness not unique to President Obama).