I am in the UK. Could I set up a free to enter contest (requiring the
skill of the entrants each week for a period of say, 3 months) that
allowed participants from both the UK and America (possibly Australia
too). Each contestant plays against each other and would be required
to make choices based on real life events to progress in the game each
week. The contest would end at a predetermined date, with the winner
receiving $1000 in prize money.

The game is not a lottery or a sweepstake and there is no
"consideration" required from the participant (therefore not
gambling).

Would this be possible at all, or is this likely to turn into a legal minefield?