I understand the sentiment, but the Union was in no position to fight a civil war immediately after, let alone during, the Revolution. The Union nearly collapsed from debt in the early years, and if the northern states tried subduing the southern states, the British, Natives, and maybe even the Spanish would all take advantage of the disarray to put the rebellion down.

I do think more could and should have been done, but the whole point of the "meager defense" I put up was the lack of foreknowledge on their part.