“In the US, they do it on a Motzei Shabbos since most people will not be affected until Monday (and m/w they have time to get used to it).” For this same reason, in Israel clocks changer on a Friday, so people can recover from time change over Shabbos. Even the secular government knows better, not to change clock on Shabbos when people are resting, to avoid Halachic issues with adjusting clocks on Shabbos itself.
