That's 67 total ms for xCloud, not 67 additional ms. So it's only like 4ms more than playing Halo 5 locally on an Xbox One. And the nearest server in the test was 400 miles away. That's pretty impressive, and good news for me since Microsoft's nearest Azure center is about 300 miles from me.
Sure it wasn't a PC behind the curtain running the 'cloud' :) I would take these results with a grain of salt. It's not that hard to get a dedicated line for demonstrations like this.
The distance isn't the problem, a round trip through fiber over 400 miles only adds 6.14 ms. Yet if your stuck with your pedestrian connection, a lot of hops and traffic jams will quickly add to that number. So perhaps Google's 166 is a better indication of real world results.