Actually the trucks labeled UN are on rail cars and that is because they are built here in the US. They are then sent to the EU.
UTAH does tho allow the UN to take over a building right here in the US. Many places have seen UN vehicles on the streets. Be at guard, they will try. As stated above, the UN does not have the manpower to invade. They will do it a piece at a time. Do not go for the helmet, it is strong, go for other spots.