CiviCRM API V3 : Translate Two Digit State to State_Province_id?
Try this:

$result = civicrm_api3('StateProvince', 'get', array(
  'sequential' =&gt; 1,
  'abbreviation' =&gt; array('IN' =&gt; array("AL", "MD", "FL")),
  'country_id' =&gt; 1228,
));


Note that you should specify country_id as state abbreviations are not globally unique.