It takes about 8 to 12 hours to drive across Texas, which is longer than it takes to cross Germany. France and Germany have different laws, and so do Texas and New Mexico. Once you realise that the USA is essentially 50 different countries stapled together, it makes a lot more sense.

Their tipping culture seems insane to me.

It works the same way it works in Europe between countries in the EU. The laws are similar enough that it isn't a problem in most cases. There are also efforts that states do to harmonize parts of the law. It keeps the peace because states have different ideas on how to govern themselves.

That then plays out to taxes, as some states have a far more active government than others. So, the states, counties, and municipalities have their own ways to generate revenue to provide the services their communities want.

Most people never leave their home town, let alone their state.