Regarding the effects on Asia, I think they would be minimal. The settlement of the Americas involved a relatively small number of actual immigrants. There is no reason to believe that the millions of people subsequently born in the Americas would be born in Asia. I don't think population densities in NE Asia would be substantially higher. If there was any Pleistocene settlement from NW Europe (a very controversial and not well documented theory
The absence of humans in the Americas until the first millenia AD would have a major impact on the flora and fauna of the Americas, and major impacts on the food resources available to be transferred to the old world: staple crops such as maize, potatoes, tomatoes and, many varieties beans and squashs well as a few other luxuries and drugs such a chocolate would not exist. Population growth in Europe and elsewhere might be limited by this.
Eventually advanced cultures from the old world would reach the Americas, and they would probably find it more difficult to settle many areas without the benefit of all the native crops that evolved/were bred and the technologies associate with their propagation as well as resource and geographic information that could be extracted (willingly or otherwise) from the inhabitants. Pleistocene megafauna might (or might not) still be present and they would fairly quickly be hunted to extinction or near extinction for the same reasons it is believe PaleoIndians had a lot to do with this in OTL.
So you think that Asia might have a million or so more people? Not much more?
Also do you think that Vinland would have failed do to undomesticated plants