there absolutely is a post 9/11 world, because 9/11 affected a country that has outsized power and influence on the world stage. Relevant to this discussion, massive changes in financial regulation significantly impacted how money moved and how trade can be co ducted internationally. Let's also not forget the decades long wars in the middle east triggered by 9/11, with all the netions involved and the widespread feonts the "war on terror" engages in. Especially in the Middle East, 9/11 mattered, because it mattered to the US and allies, and the US and allies responded with invasions.