> One requirement for having solid laws, would be some sort of compulsory security audit of the code by independent experts.

This doesn't exist in the U.S. financial system. Maybe it should, but honestly it is such a stronger requirement than anything close to what we have currently, and I imagine it would be impossible to enact on a resistant market (try defining "independent security experts"... oy).

As a German, you may want to brush up on your understanding of U.S. law. First, if you're a mail order business in California you don't have to pay attention to any other state's sales or use tax laws unless you have a business presence (such as an office) in that state. As a California shipper shipping in-state you need to look up the destination zip code's tax rate, true, but it's county-by-county and you can do it for free here: https://maps.gis.ca.gov/boe/TaxRates/

Second, if you want to avoid even this annoyance, you can start your business in one of the five states with no sales taxes including New Hampshire or Oregon, meaning you never have to collect any sales taxes. Third, if you do have offices in other states, you can buy some relatively cheap software that takes care of billing for you.

I'm not saying this system is perfect or even that it'll continue given the pro-Internet tax forces in Congress, but nevertheless I don't think your description is accurate.