Harry is still a “prince” in the Royal Family. As such, he is precluded from involvement in his own nation’s domestic and international politics, and even more so in a third country such as the US which has hosted this bum. This certainly makes it look like the Royal Family is taking political positions in the United States; does the Prime Minister of our supposed “ally” go along with this??
You are absolutely correct and yes, the P.M. ( who is a JERK! ), and Parliament have a say so...IF our president complained, in a formal letter to them.