how is this 1 person suposed to handle tax law in over 2000 different locations?
They don't. The bill passed requires the internet sales/use taxes to be uniform for the entire state. So there are less than 50 sets or rules that the retailers have to deal with.
Secondly, you could say the same thing about credit card processing. How can a small mom and pop deal with the rigors and complexity of PCI compliance? They don't - they contract out the work to a credit card processor, and don't worry about it.
The same thing will happen here. These credit card processors already have the ability to handle collecting sales tax in every possible jurisdiction, because they already work with thousands of mom & pop's who combined span every possible tax jurisdiction. They will do all the work of computing, collecting, and tabulating all the taxes, and at most the mom & pop's will just have to file the forms that the processors give them.