The Pollack connection is good, but the Cash/Carter one - slightly, hmm, dunno...
I love the song actually, but Jackson, Mississippi - to me - conjures up segregation, freedom rides, lynchings, and a rather backward attitude to race relations. I hope I haven't offended anyone with this - just saying what comes to mind when I think of Jackson MS.
Then again (I'm dead indecisive, me), I'm not even sure I'd think of Jackson the city if I heard the name on a boy...
I know of a little boy called Jackson, and I didn't even think of the city; rather I thought that he had a rather 'of the moment', surname-y type name.
I think you will get a different response to the name in different countries (I'm not in the UK - I'm in the Antipodes and there tends to be more of a tendency to follow US trends here than there is in the UK).