Gee, not sure if anyone does anymore. Delta is about the only mfg'r left that manufactures some tools in the US, but not sure if their drill is one of them. Doesn't matter anyways, I have their 14v shopmaster and wouldn't recommend it at all, it's a pos.
bcelect is right. And all of those companies really do go a long way to make sure their tools are manufactured to last. There is a reason why a Milwaukee drill costs $200 or a Porter Cable saw costs $250.
As a tool junkie, trust me, these tools can take some serious abuse. I have a 7 year old makita cordless drill I still use daily or a 5 year old Bosch circular saw that won't quit.
Sometimes you will see tools such as black and decker or ryobi and craftsman all being made by the same factory. They may look the same on the outside but they are NOT the same tool. Where one my use nylon bushings, the other uses ball bearings etc.