Hi Andreas, here is another German living in the US (Maine).
I tend to think that "call" in those cases you mentioned just stands short for something else. Take "good call" as in we agree with the decision of an umpire/referee in any sports event just means "he said it right".
Btw, have you seen the Panthers last night ?

MW: call
10 : a decision or ruling made by an official of a sports contest; also : DECISION 1 <a tough call to make>

AHD: call
13. Sports a. A decision made by an umpire or referee. b. An announced description of a game or race, as by a sportscaster.

SUPPORTED.

Die urspruengliche Quelle scheint der Sport zu sein, darum wuerde ich dies ebenfalls aufnehmen. Ich kenne es zwar ebenfalls in der Form von "It's up to you. Your call!" == "Your decision!" und MW stimmt damit ueberein, aber ich wuerde es dennoch als umgangssprachlich bezeichnen.