About as problematic as a Jew celebrating Easter.
But I hope & trust that it wasn’t problematic for Michael Bloomberg to attend this parade on Shabbos.
As per Halocho, I am Don him leChaf Zechus, that he walked to the parade from Gracy Mansion not to desecrate Shabbos, and even if he did carry something at the parade, I am sure he was relying on the “5th Avenue Synagogue” Eruv, and I am sure that he or 1 of his aides called in on Friday to verify that the Eruv was intact & operational.
Next year after he has left office, he shall have to decide if he is more interested in spending the day on 5th Avenue attending St. Patrick’s Day Parade, or maybe more interested in spending that same day on Rehov Ben Yehuda watching all the costumes on Shushan Purim.