Starting the war for those aims is a war of aggression, removing the Taliban is setting up a friendly government, removing their right to police is a removal of sovereignty.
Really confused what you're going on about, you keep saying I'm wrong but don't try to say why.
Precedent? This isn't a court case. I begin to see the problem here: You're misapplying a historical template. This isn't 19th Century British Empire - the US had an iron-clad casus belli in Afghanistan, and to ignore that is to completely mischaracterize the situation.
"This isn't a court case, they had an iron-clad case for war." The only point of a cassus belli is to justify your war of aggression, if someone declares war on you the case for it is clear.
And no, the cassus belli was not iron-clad. There are only three legal ones under current law. Defense, defense of an ally, and a UN approval. First two don't work, Afghanistan hadn't declared any wars, and the third never happened.
Really confused what you're going on about, you keep saying I'm wrong but don't try to say why.