“At no time did these British forts become a casus-belli for the US government, which waited patiently until their evacuation by Britain could be negotiated peacefully.”
That’s a silly statement, since they had already fought a war with Britain and won! Of course they didn’t need to declare war again, the British were beaten and that was acknowledged by both sides.
And yet, despite Brits losing the war, and despite their signing a peace treaty promising to abandon Brit forts on US territory, THEY DIDN'T LEAVE!
They stayed in those forts, some for 30+years (!), in order to protect their economic interests and their Indian allies.
And what did the US government do about it?
Nothing! We let them stay and do whatever they wanted to do for decades, until, one by one, opportunities presented to negotiate for British removal form those forts.
And that is the model Confederates should have, would have followed, if their main interest was in preserving the peace.
But of course, peace was not their first concern.