I don't think there is an exact phrase for what you want, whether in English in general or specifically in American English, but you might consider describing such a person as (from Oxford Dictionaries):
(Of a person)
Relentlessly compelled by the need to accomplish a goal; very hard-working and ambitious:
"my husband is a driven man"
Directing a great deal of attention, interest, or activity towards a particular aim:
"Darren knows what he wants and he's very focused"
"he seems to be very focused on the new challenge"
"the need for more focused research"
Having made a firm decision and being resolved not to change it:
[WITH INFINITIVE] "Alina was determined to be heard"
Possessing or displaying resolve:
"Helen was a determined little girl"
"a determined effort to reduce inflation"
Having or showing determination or resolve:
"the purposeful stride of a great barrister"
As for antonymous adjectives, you might consider:
Without purpose or direction:
"an aimless existence"
Unable to concentrate because one is preoccupied by something worrying or unpleasant:
"Charlotte seemed too distracted to him much attention"
I don't think you'll find anything that is a perfect fit, though.