By the time the US entered WW1, it had been over a century since England had attempted any serious takeover of the Colonies. During that century, America had fought a massive Civil War and the evils of slavery really started to overshadow any faint memories left over of British control.
By WW2, there weren't even any Civil War survivors left alive (if they were, they would have been too young to really remember anything about the Civil War), and the atrocities of Great Britian were long forgotten and easily overshadowed by the threat of Nazism and then Communism.
At that point, Britain could no longer exert any control whatsoever over the US and could only attempt to influence us by appealing to our sense of justice and morality. Kind of like an aging parent asking for help from a rebellious child.
Also, I think you will find that Americans don't put nearly as much stock in symbolism as the British do. There might still be a Mace in Virginia, but I'm sure no one there sees he/she/it (?) as anything more than a tradition with no real power.
What exactly is a "Mace" anyway? Because when I think of a mace, I think of this...
...and it's funny to think of some politician in Virginia waving this around every time he or she speaks.