I ask as one who knows little of these things. If two magnets are forced together South-to-South and North-to-North they try to get into a North-South alignment. They don't 'like' this orientation. Could not the same thing happen if a strong enough field approached from space? That is, could Earth wobble a little on its axis as the two fields interacted?
Yes, it's all a matter of degrees ... having said that, it would take an awful lot of 'matter' hitting the magnetosphere and ionosphere to have an effect. We are more likely to see the earth's magnetic field change due to internal forces (in fact, it moves yearly, in fact, it moves daily) ...
Daily Movement of the North Magnetic Pole (Including diagram)