I smell a lawsuit... as soon as the apology is issued, the lawsuits will start!
DING, DING, DING! We have a winner! You've caught onto the game.
The reason why neither Clinton or Bush issued an apology, is because an apology is an acknowledgement of responsibility. If the PRESENT DAY government of the US issues an apology, the next step is a lawsuit in the World Court to get reparations.