This is a knife in the back of internet retailers - it will force them to handle sales taxes for at least 50 government entities, whereas a brick and mortar business only requires they handle a single set of sales taxes, for the community in which they are physically located.
Every supply house and manufacturer that ships their products to end users outside their state or works outside their state has dealt with paying taxes to sales they make in those other states and has done so with normal accounting systems for generations.
A retail store with one location and over the counter sales is the exception rather than the rule.
Many, many more than that. For instance, in Tennessee, there is a state sales tax rate of 7%. Then, the State allows a local sales tax of up to 2.75%. Some counties add the full amount, some add less. So, you will need to have the sales tax rate for all 95 counties in Tennessee, and update whenever the sales tax increases. Other states have additional municipal sales taxes in certain cities. The number of municipalities to keep track of are huge. Someone will develop a database and the online retailers will pay a fee for access to the database, so you can put in the customer's zipcode and the proper sales tax will be added. So, in addition to the sales tax, online retailers will be paying the fee for the sales tax database as well as shipping costs. I suppose that is suppose to 'level' the playing field?