I posted something similar on FuckJerry, but I've been thinking a lot about this... since I joked "what would I do if I threw an '00's party as a followup to the '90's party I threw a few years ago":
The 2000's:
-9/11 and an increased patriotism in America
-Tacky, campy 9/11 propaganda (the crying eagle, country music like "God Bless The USA")
-War, war, war. The "War on Terror". War in our games, war in our movies.
-Hip-hop hits its peak in the early part of the decade, everyone you know is listening to Juvenile and Ludacris, even the goody two shoes white girl down the street
-Hipsters
-The Exurbs
-Minimal Techno
-Minimal aesthetic, curvy white and bright primary colors being the popular look for electronics and interior design
-Guidos becoming mainstream, blowout haircuts, Ed Hardy shirts, Affliction shirts
-Lots of shirts with skulls and fleur-de-lis on them
-Poker (especially Texas Hold Em)
-MMA becoming huge
-Thick-rimmed rectangular glasses
-America loses some of its spotlight to BRIC and developing nations
-Globalism becomes much more popular, along with musicians mining obscure regional sounds (see: Diplo and Pitbull)
The 2010's:
-Electronic Dance Music FINALLY becomes huge in America
-Rap seems to be much less popular
-A new wave of feminism, politically correctness, civil rights, and a backlash to this
-Internet culture/meme culture hits mainstream
-Rustic "farmhouse" look becoming popular for interior design - exposed brick walls, found objects made into tables, 'restoration furniture'
-Manbuns
-Nationalism as a counter to globalism
-Nerd culture becoming mainstream (comic book movies, cons, anime, esports, gaming, memes, even D&D to a lesser extent)
-White gentrification of the city while the suburbs diversify