I think a permanently divided USA would have been a blessing for most of its neighbours, near and far, because the two halves of it would have devoted most of their paranoia and military aggression toward each other ever since, thus taking the heat off the rest of us, as it were...and they'd not have become the Superpower that the USA is now.

As a later side effect, Germany and Austria might also have won the First World War on the continent of Europe (they'd never have seriously threatened the UK), and that would have removed any possibility of the Nazis ever coming to power, while I doubt it would have made any appreciable difference to the general welfare of either Englishmen or Canadians in the years following. It just would have been another humiliating defeat for France, that's all, and they'd have survived it.