Strange framing.
Currency manipulation is meant to benefit the country doing manipulation (in this case Switzerland) at the expense of another country (in this case U.S.)
It's very much the role of U.S. government to protect U.S. from other countries trying to do harm to U.S., be it by bombing U.S. territory, tariffs on U.S. goods or currency manipulation that economically hurts U.S.
You could present an argument that Switzerland wasn't trying to harm U.S. economically via currency manipulation but instead you're trying to delegitimize the very idea that U.S. can defend itself from other countries trying to harm it economically by pretending that it's purely internal affair that has no effect on U.S.
Currency manipulation does hurt U.S. and that's the reason U.S. has the right to push back on it.
I said Switzerland was labelled a currency manipulator - its attempts to devalue the Franc was in response to the sharp rise in its value as a result of Covid and the markets plowing money into safe-haven assets. This presented a real problem for the country at the time, and the primary dynamic at play wrt exports in the country is actually between CHF and EUR, not CHF and USD. The US designation was widely considered arbitrary iirc, putting Switzerland into the same grouping as countries like China, which have vastly different reasons for devaluing their currencies, and arguably ones more in line with what the US was actually supposedly targeting.
So I haven't claimed that Switzerland is a currency manipulator, nor that this would be a good thing, nor that its efforts to devalue its currency had anything to do with the US. I don't see what the contention is here - unless it's that only the US is allowed to be "independent" (i.e. above all international law), here wrt the ICC, while other countries must curtail what is in their national interests (like not having their export markets decimated) for fear of provoking this one special, privileged land?
If the argument is that the US can enforce its agenda on other countries and they must just suck it, then sure. But that's not an argument about fairness or what's right, that's an argument about what to expect from the actor with the biggest stick.