Alternate realities and cross-dimensional travel, not such a thing. They were there in an alternate New York, weren't they? Even cloning wasn't so impossible; Huxley had written about a dystopian society that employed genetic engineering back in the thirties. But giant killer robots?
"Huh." Steve sat back in his chair. "Robots. I think the closest I've ever seen is Mr. Stark's armor."
His was clearly not a world with an Ultron or a Vision.