Really? Weird. With all these new changes I find that now more than ever I wind up on the American site because of something I've clicked somewhere along the way.
That big Canadian flag in the middle of the page immediately lets me know when I'm back in the right place (the wrong place for you though).
All you can do is quickly go back to http://www.ebay.com/
I have my Canadian ebay saved in a Shopping folder in my favourites bar. Any time I get 'lost' I simply click to get back 'home'.
Nice meeting you! 