I remember The Next Doctor having the question of "why didn't this giant mecha Cyberman appear in the history books?"
I forgot what the Doctor said in response.
Moffat explained that with the cracks in time.
However, he's done nothing to explain the frankly ridiculous shit of the Statue of Liberty waltzing around New York or a huge dinosaur in London. I guess he's stopped worrying so much about that sort of thing, so now in retrospect... people shouldn't've been very shocked when that huge alien spaceship in Christmas Invasion appeared.
"Oh, yes, we get this sort of thing all the time, you know. Best to carry on."