I buy my boots from midwest boots and Workboots.com.
Both list the COO very clearly, but they don't always have every model from every company nor to they stock every single manufacturer.
Still they do make it clear which is good, midwest prices aren't always the best but they often throw in a free T shirt or bonus pair of good quality American made laces with Thorogoods and in general they care about American made boots most.
Btw there are some companies that do lots of contract production and of course this means a number of American brands that do not have their own manufacturing facility.
Weinbrenner ( who owns and created the Thorogood line around 1918 ) manufactures boots / shoes for many other companies and used to make the work and sport line for Fleet farm.
LL bean boots are made by Chippewa who is now owned by Justin.
Maybe I missed something, but I didn't see Ariat boots on the list, Tecovas, Peter Limmer & sons,nor did I see Lacrosse rubber boots, or Dunlop rubber boots.
They also left off Georgia boot, but I'm not sure if they have their own factory or not.
There are even more, but I suppose the fact there was enough for them to forget some is a good thing.
There may be far more options for imported crap today, but there are also plenty of American made boots to choose from too.
You won't pay under $175 unless they're on sale or it's just a pair of rubber wellingtons which tend to start around $20, but the American options are worth it.