The cultures of reality TV in North America and elsewhere are way too solidified for any radical changes to be made at this point. You can't undo a decade and a half of history just because of what other countries are doing. Everything in the US (and Canada) is a reaction to Richard Hatch winning Survivor, and everything in the UK is a reaction to Nasty Nick getting expelled at Craig winning. If BBUK let the HMs discuss nominations and actively play the game, not only would the general public not respond well to it but the HMs really wouldn't know what to do. Just rewatch the first week of BB13 and see how that went.
And even so, if you like the BBUS format just watch BBUS and BBCan. If you like the BBUK format, just watch BBUK and CBB and BBAU
I don't think one format is inherently better than the other, but I will say that I think the best seasons of BBUK are better than the best BBUS seasons.
I also think BBCan is growing a little stale and has lost the magic from the first two seasons, but that's for another discussion.