As an example of how complicated this can get:

Many states and municipalities tax "cookies" differently than other food items. For a long time Fig Newton used "A cookie is just a cookie, but a Newton is fruit and cake" as their most prominent add copy, and while some people have referred to Fig Newtons as cookies, the people who produce them don't. Would you like to be the person in charge of figuring out, for every jurisdiction in the US where its relevant, whether or not a Fig Newton is a cookie based on relevant law and precedent? There isn't a consistent answer that applies everywhere. And that's just one product among the many, many that Amazon sells.

Sort of. As I understand it this law would require amazon to start collecting sales tax. It does not mean amazon would be paying more themselves. Only that customers final bill would now include the local sales tax.