mod is fun but far too easy - playing as Union of Britain I have liberated USA, Canada, the German Empire, Ottomans and the Russian Empire - all before the end of 1941.
I just played a game with UoB (a great nation to play with, to be sure) and while I got Canada, the mainland was lost thanks to the incompetence of the CoF. That means an eternal stalemate, unless you have the patience of playing for 10 more years to industrially overtake and outproduce the Germans. The default UoB doctrine is quite shit compared to the Germans', at least it seems that way to me.
Then again, if things do go right, why are you expecting to have a challenging game with one of the most powerful and most user-friendly nations of the mod?
And now for some comments of my own:
Should the UoB really have to trudge all the way to Winnipeg to defeat Canada? Makes sense for a Combined Syndicates victory, where it's right on the border, but for the UoB, the walk alone (even with MOTs) takes months, not to mention the few stragglers who try to stop you. Wouldn't it make more sense to scratch the Winnipeg win condition and just have all the major cities in the east captured to win? I mean, anyone who has captured Halifax, Montreal, Ottawa and Quebec has won against Canada already.
Then there's New England. It fought alongside Canada, getting defeated of course, and it stayed on my hands. There should be a way to return it to the Combined Syndicates, if it was victorious (or even if it's still fighting, with a "wait for the end of the civil war" option), or establish a Socialist Republic of New England by event. I'd say this is worth addressing because Canada and New England fighting together against the UoB is a pretty common scenario, and the civil war still raging when I invade is quite likely.
In addition, if Canada seizes Alaska, I retain Alaska after the reactionaries are defeated and the SocRep is established. I don't have much of a problem with that, after all, there's oil there and even a few bases, but in case the player doesn't want to bother with it, there should be an option to hand over Alaska to Socialist Canada, possibly with integration events afterwards to make Alaska national territory of the new Canada.
While we're there, Ireland should also have integration events. Okay, I get it, there were bombing campaigns and Irish industry has been heavily damaged, but the Scots and the Welsh are having fun in the Union. Why don't the Irish eventually settle down too? I mean, Syndicalism is all about internationalism and erasing national boundaries. For added flavor, there could even be Irish candidates in later TUC election events (or cabinet choice events, or whatever) if Ireland is in the Union. But that's secondary.
There is a war between Poland and White Ruthenia over the ownership of Brest Litovsk. I haven't bothered to check if there is a surrender event for White Ruthenia, but there isn't one for Poland and there should be. In my case, WR was allied with the Russian Empire and Poland was destroyed, leaving WR with all of Poland. A bit ugly and nonsensical, I'd say, for an AI White Ruthenia.