“Heads on pikes” is used as a hyperbolic shorthand for any kind of public shaming, especially when someone is fired.
But “Mount their heads on pikes at the corners of the White House as a warning the way they used to do to traitors in Tudor England” is nothing close to a common expression.
But “Mount their heads on pikes at the corners of the White House as a warning the way they used to do to traitors in Tudor England” is nothing close to a common expression.