XB1 competing with PS4 in US alone shows it will end up well ahead of WiiU WW.
Combined the 360/PS3 userbase last gen in US was 70m~ even a 40m/30m split to PS4 (which isn't even close to being generous or sample like from current figures (3.05m vs 3.76m).
Then add on the fact US is 50% of Xbox audience and you're looking at 45/50m lifetime for XB1 as it currently stands (they could still take back US if they tried harder).
Point being, WiiU is going to struggle to hit 20m, it's struggling in every region. XB1 will do more in US than WiiU will WW lifetime by the end of this gen. Heck, it's already sold more in US this year than WiiU has shipped units WW.







