I understand not every decade was a clean break, but each decade has fairly distinct defining properties. It feels like most of the 21st century has been a single run on with smaller changes. I know sometimes the definitions don’t come into focus until later, but I’ve been around since the 80s and I can distinctly remember the changes between the 80s, 90s and 00s as they were happening.
I think this is certainly one important element to it!
And when I think of America, I actually can see distinctions in 2020 / 2010s architecture compared to 2000s or earlier - America can afford to build where Britain and other european countries can’t, really. Or won’t, because of environmental reasons and lower population growth.