Any old run-of-the-mill (not even high office quality) sociopath will easilly tell you “I’m so sorry” whilst not at all being sorry, if they think it will get you to do what they want.
It means nothing when the kind of people that seeks power say anything that helps convince other in a way that furthers their aim of reaching or keeping power.
Even if you’re still willing to given them the benefit of the doubt, this being the office of the President Of The United States there’s lots of intelligent people there and they have lots of access to information and advisors to be well informed, so what they do are “informed choices” (or at least have the greatest opportunity in the World to be informed) by which point whilst that “sorry” about their support on the first week might made sense, it makes no sense whatsoever after that when it was increasingly clear even to us “plain old citizens” what Israel was doing.
Both in terms of a generic risk assessment on such individuals and on a logical analisys of their actual actions and words in this situation, one can only conclude this “sorry” is complete total unfelt bollocks uttered merely to manipulate people to get their votes.