Do as your fellow countrymen do (according to facebook):
Leading into the final match between Argentina and Germany, chatter and polling are just starting to pick up. Current data indicates a trend of global support in favor of Germany (55%-45%). Argentinians obviously support Argentina (95%-5%), Germans support Germany (95%-5%) and
the Netherlands lean towards their continental neighbor, and probably against the team that beat them in semi-finals (81% support Germany, 19% Argentina). The Brazilians are stuck between a rock and a hard place: they can either support their regional rival, or the team that just beat them 7-1. In this case, regional history weighs more: 71% of Brazilians support Germany, 29% Argentina. Finally in the US, things are split exactly in half, with 50% supporting each side.
https://www.facebook.com/notes/facebook-data-science/world-cup-fan-migration/10152377138198859