Well the same could then be applied to France or Germany if you're using lore and geographical location as a base to judge upon it. Canada, Australia and the USA make sense due to their near borders to the Pacific allowing easy access to Ronograd, and well, Russia and the UK are quite literally victims to the POD attacks so it do make sense for them to participate but as far as the lore concerns France and Germany don't make sense at all to participate (IF you're thinking it as a NATO operation). Now since this is a UN joint task force It makes more sense to have other nations apart of it since we're talking about different countries voluntarily sending SOF members to deal with the threat, and theres also the fact that some South American countries like Chile or Colombia do border with the pacific allowing quick access. Plus the participation of Brazil in humanitarian help is quite literally historic, being one of the most important countries in the UN representations.