Western Mountaineering or Feathered Friends is the next level. Not sure there is anything better. Both made in US. I bought a WM bag from Moosejaw. Between % back in points from MJ and another % rebate from Active Junky, I thought it was a pretty good deal.
Another option under $400 would be a Kifaru slick bag. I have never used one but they are under $400 and according to their website the long are good to 6'7".
Under your budget but may be a little bulky for some but its hard to beat a Wiggys bag for the money if you have the room. I've slept well into the teens in my regular/wide 20deg ultralight and it comes in about 3.50lb. Not real heavy but they are just not as compressible because of the lamination on the insulation. Thats the only downside, otherwise they are pretty bombproof and very warm for under $200 on sale. Ive been using and washing mine regularly for a few years and never had a issue.
I run a BA Summit Park 15 (long). It’s a touch heavy but I prefer a roomier bag and that worth it to me. Use a S to S Comfort Plus insulated pad with it.
Mtn Hardware makes good bags well within that price range, if you decide to go that route hit me up and I'll send you a coupon code for 20-30% off on their site
If you can step up another 150.00 a western mountaineering badger MF is about as good as it gets. I got the 6’6 version (I’m 6’4) and it feels awesome.