You have not provided enough context for anyone to give you useful advice. We would need to know your hourly or daily rate and to basically see your resume to have any chance of giving a rate range. There is also the issue of taxes which make comparisons less straightforward.

That said, I think you can generally expect IT pay to be higher in US major cities than almost anywhere in the EU. The US also has the concept of consulting. That runs the range, you could be working for a body shop agency for no more pay than a salary where the agency takes up to 50% of the client’s rate. You could also be an independent consultant where you run your own company and directly market and contract with your clients for 2 or 3 times the pay. The latter takes a personal network and a reputation. If your current clients pay you well, why not just properly structure things and work for them from the US?

Besides pay, there is the issue of cost of living. You could have the option to live in a fairly rural area and commute into Princeton. Cost of living can be fairly low in the US outside major cities or some of the highest in the world within them. It is a big country with much variance.

One last thing: you will find that the US is basically still the barbarian lands in comparison to Europe, history has a long arm. That can be good or bad depending on you, but don’t be shocked when you find out that the country is bordering on anarchy in comparison to Germany, expect it.