If a US company hires you in Germany, either you get hired by their German branch or a personnel service provider based in Germany; and thus get paid "competitive" salaries typical of the country. Or you need to have some kind of setup where you are a freelancer or such and you figure out the taxation and statutory insurances and such on your own, which I'm not familiar with (my freelance IT consultancy side-business is rather simple because of small scale and only domestic customers). That will probably work, and if you manage to get a senior Silicon Valley salary, you would probably come out ahead by a bit after taxes and insurances. But you would probably need good tax advisors to avoid stepping in expensive loopholes, and if you work more than 80% for a single employer, the tax administration will be on your case because false self-employment is a possible method of tax evasion and has been outlawed.
If a US company hires you in Germany, either you get hired by their German branch or a personnel service provider based in Germany; and thus get paid "competitive" salaries typical of the country. Or you need to have some kind of setup where you are a freelancer or such and you figure out the taxation and statutory insurances and such on your own, which I'm not familiar with (my freelance IT consultancy side-business is rather simple because of small scale and only domestic customers). That will probably work, and if you manage to get a senior Silicon Valley salary, you would probably come out ahead by a bit after taxes and insurances. But you would probably need good tax advisors to avoid stepping in expensive loopholes, and if you work more than 80% for a single employer, the tax administration will be on your case because false self-employment is a possible method of tax evasion and has been outlawed.
If the client you're consulting for has no presence in Germany then it cannot possibly be false self-employment, surely?
False self-employment is judged solely by whether you spend 80% or more of your worktime working for a single employer.