Here is what I have read, heard, gathered, take it with a little skepticism...
If we are talking new cast iron....
Lodge is the only new American Made Cast iron. It is premium quality, density, finish, pre-seasoned, and about a 20% price premium. Amazon is having a great sale on 12-inch deep Lodge Duth Ovens right now. Free shipping, $50!
Camp chef is next. Good quality control China made. Finish, density, and pre seasoning is almost as good as Lodge.
The upper two, I would have no problem buying sight unseen.
All others are made around the world in various places other than the US and have inferior quality control. They may be OK, but must be inspected to make sure you get a good piece. Some are thin, warped, chipped, have ill fitting lids that do not seal, and not good pre-seasoned. Metal finish can be uneven making it more difficult to season and make nonstick. These are about 50% less costly than Lodge and Camp Chef.
There are other older, used US made Cast Iron. Some of those are even superior to what is being made by Lodge now. They were finished finer and lighter... Stamped Griswald, Wagner, and some others. But I can't find them in my area and I don't know much more about them.
Here is a link with much more info...
http://www.castironcollector.com/collecting.phpMy advice... Get the lodge 12-inch now! Practice, play with it, you will not regret it. I got mine about a year ago. I wish I had found them earlier in life. I cook with mine at least 3 times a week, if not more!