AFAIK the law in the US is much more arbitrary in the sense that a lot of it is case law. Until such a case has been before a jury, and jurisprudence has been established it's basically a coin toss.
The thing that may feel arbitrary is simply the fact the laws in Europe actually enforce privacy, whereas a company, and people, form the US expect that these laws are teethless.
The thing that may feel arbitrary is simply the fact the laws in Europe actually enforce privacy, whereas a company, and people, form the US expect that these laws are teethless.