What are the key differences between brats in Germany and the USA?
I'm sure it's down to how the meat is ground (if the issue is texture), and what spices are used (if the issue is flavor). It's less likely that the meat is totally different--though you never know. 

There are about as many variations on any given type of sausage as there are people that make them.

Your best bet is to either keep trying to find a place that makes them the way you like them, or learn to make your own (fun and easy). There are a lot of books out there on sausage making, and it's not hard to do.

You will still need to learn to identify the characteristics of the wurst you liked so that you can, over time, learn to tell which sausage recipe will get you close, and so that you can adjust or combine recipes until you get the taste you're looking for.