I tire of those who believe the US can even think of arresting heads of foreign states. If Merkel is ever in an orange jumpsuit it will require the people of Germany indict and try her. The US 'arresting' or taking into custody the Queen of England was another bullshit theory floated around here. The US can clean its own house and provide information to other countries, but any attempts by the US to arrest, detain or even indict heads of sovereign states not subject to US laws, or even international law, would represent an act of war, and would be responded to as such.
Wow Germany is not Sovereign? Sauce please. I suggest you consider that they have been signing their own treaties for decades now, have their own standing army, navy and airforce, and pass their own internal laws with no US/Allied intervention.
https://www.history.com/this-day-in-history/allies-end-occupation-of-west-germany