No, you can totally do that if you put up with the severe inconvenience of being an economic migrant for that time.
(Immigration bureaucracy, distance from family, working and living in your second language, navigating an unfamiliar system, immigration bureaucracy, and the risk of being arbitrarily deported)
Seems far more likely that someone would leave Germany, earn a higher salary in the US for a while, and return as soon as a serious health threat made the disadvantages of the US system clear.
Presumably Germany has some sort of system to tax imported wealth to handle these scenarios.