Ridiculous how all the major cities are rebuilt as before, in 20 years

Lol, I didn't even think of that. More than that, with the population so decimated, who would be occupying those new buildings. The death toll globally must have been hundreds of millions.

There's a balance between being a direct sequel to a previous movie that younger audiences might not even remember, and needing to have things look familiar to such audiences based on the world they actually live in.

ESD was formed in 1998. and after that after all countries has united like never before there is a lot of going off which allow us to build faster.

I believe to for example, old brick or rock building like Taj Mahal is all made of metal construction with some facade. With that whole process of rebuilding is a lot of faster.

But on other side, some cities didn't rebuild at all. This is Las Vegas:

https://c2.staticflickr.com/2/1663/24276688802_425ef5139f_o.jpg

Moon base becomes operative in 2009. but alien weapon arrives just before arrival of Harvesters.

Yeah, I only suspect that was remotely possible was because of all the alien technology acquired in 1996 that was quickly used to make construction 10 times faster than it was before... But even then, it would take years to reverse engineer the tools and capabilities of the City Destroyers, Troop Transports, and Attack aircraft. Also, the entire world united would accelerate things too, but eventually there would be inevitable conflict and rebellion.

But even then, as some others have mentioned, entire cities rebuilt, with towering skyscrapers 5 to 10 times larger than what was previously there, is crazy. The world lost millions of people in 1996, maybe hundreds of millions, just who is living and working in all these new skyscrapers?

In real life it took some 15 years for One World Trade Center to be rebuilt, and that is a single 110~ floor skyscraper....