If an ability that affects all players is used, then does that make each player a target of the effect?
I.e. Is Guttersnipe activated am I able to change the target of the ability?
No, only things chosen for the word "target" are targets.
One notable exception is Aura enchantments, which are cast targeting the thing you want to enchant even though the word "target" does not appear on them (rule 303.4a).