I'm no wisteria expert but my vines are pretty much indestructible. I have a couple Amethyst Falls. It blooms on new growth so cutting the old vines shouldn't be a problem. Did you leave any of the growth coming from the trunk? If not that could be a problem because the new shoots will grow from them. Hopefully someone with a bit more knowledge about wisteria will post an answer but I don't think that you killed it.

Yes, I did manage to leave two thumb sized branches with foliage at the top. I was trying to shape it like an umbrella and those were the only branches that maintained that shape. I did read that with overgrown wisteria you should cut it back drastically and then treat it like a new vine with supports etc. (I read that AFTER the drastic cutting I did on my own though...but I do feel a bit better....)

I have a similiar question (hope you dont mind me piggybacking) When would be the best time to prune back a wisteria? mine is trying (not successfully) to trail on a pergola, but when it's at the top, it just grows straight up and doesn't seem to seek out the pergola itself. It's hard to get up there to try to pull it through when it's so tangled. I'd love to wack it back to at least the top of the pergola.

BUT WHEN? does it matter?

Cut them back severely - BEFORE January - later will remove the flower buds.

Don't pull the wisteria through the pergola. It will end up pulling the pergola out of the ground. Use string to tie the branches above or outside the pergola framework. As they age, the branches will become rigid and won't need the ties.

Establish the framework, then enjoy the blooms! I love Wisteria.