There is a US-based site http://www.bestgermanrestaurant.com/ sponsored by some German food importers and cultural organizations which is somewhat comprehensive and lists my favorite places. They also have annual voting. The polls open this year on September 1st.

In 2010 they named the Old German Schnitzel Haus in Hickory, NC as #1. (I don't know if it's best in the country, but I'll vouch for the fact that it's very good.)

Two Austrian places which so far have not been mentioned in this forum, but definitely should be:
Cafe Old Vienna in Myrtle Beach, SC --- a small place in a strip mall with a fantastic cook. Delicious food!
Gaestehaus Salzburg in Lake Lure, NC --- the real thing, from Salzburg

And a good German place south of Charlotte:
The Waldhorn in Pineville, NC

Guten Appetit!