Thanks for your answers; The police man actually never wanted to see my passport, he only had my driver's licence which, however, still contains important information such as name and birthday; Therefore, they also never sent me a letter to my residence.

And actually in my letter to the judge I also wrote that first of all my cruising speed was measured incorrectly and that I did drive at "a rate of speed no greater than is reasonable and prudent." Especially considering the German highways I am using every day, I am quite confident that the cruising speed was safe;
But later I also found out that in the county (20x50 miles) there are just 5000 people living there so I do not want to wrongly accuse them but it seems like monetary aspects certainly played a big role in this case as well;

However, going to the court myself is something I did not do as I was just passing through and already had hotel and everything booked and the court only would have opened the next day and I would need to drive back a few hundred miles for that;

What is an SOP? And what does it mean? Is it possible that I will be rejected if I later apply for esta or a visa or I will be denied entry into the US?

I am currently working with a team to better forecase floodings in the greater Austin area and I might need to go to Austin for some time to meet up with my collaborators

But you are right I should probably write them and ask to pay for the original fine - even though that the speed was measured incorrectly;