France and the UK have even agreed to share aircraft carriers. We've taken a look at how military spending compares to GDP across the region, finding the European countries that might end up freeloading on the defense budgets of others. For reference, the US spends 5.25% of its GDP on the military.Oman spends 11.40% of its GDP, the highest in the world.rance and the UK have even agreed to share aircraft carriers. We've taken a look at how military spending compares to GDP across the region, finding the European countries that might end up freeloading on the defense budgets of others. For reference, the US spends 5.25% of its GDP on the military.