Apex is pretty much the only other one, but not all their bits are made in the US. Ideal also sells USA-made bits in rubber blocks, but they are not the easiest to find, and I suspect those are probably made by Apex as well.
Chapman makes bits, but theirs are specialized for their drivers, and not interchangeable with standard bits. Otherwise, the next best bet would be Germain made bits, and then bits that are made in Taiwan. I have found that Taiwan-made bits are generally quite good, but Chinese bits (especially Warrior and other cheap/no-name brands) are disposable (as in single use), and most of some of the security bits, etc are poorly made, and may not even fit the fastener correctly. I'd even say they are dangerous to uses, since they break easily.
The ones offered by DeWalt, Irwin, Milwaukee, etc are pretty good, as they are made to higher specs, but they are disposable. I guess all bits are disposable by nature, but I like to use the good ones in magnetic screwdrivers, etc, and use the power-tool-branded bits for power tools, since they are cheap and easily replaced.