I think it could be argued that if it wasn't for 9/11 the world would be at a very different place right now and even if the pandemic had hit just the same, the reaction of the US and its allies might have been very different.

The War on Terror took its toll on much of the world. I don't think the pandemic would have played out exactly the same way in a world without 9/11.

However I think it's worth pointing out that to much of the world "9/11" is not just about the terror attacks but also the immediate aftermath and the invasions of Afghanistan and Iraq. It's more of a period of time than a specific moment. Some of those things happened on the day itself, some in the days immediately after, some only months later.

Are you sure about that? because dick cheney has Iran and Iraq in his mind before 9/11.

It's a little disingenuous to use 20 years of history to say it's a more significant event and then using the follow on results. In another 18.5 years, people could be talking about how the pandemic triggered the second US Civil War, or led to a complete reimagination of US race relations, or ushered in a communist takeover or something.

How are you supposed to figure out if an event is significant or not without looking at its historical significance on the years to come?

I think this was exactly the point, you can't say one event was large due to the aftershock if the second event isn't even over (and therefore has its history yet to be written).

If you want to compare the relative historical significance of two events, you should probably limit yourself to the same timeframe. Look at how little had changed in the first 1.7 years after 9/11 and compare it to how much has changed in the pandemic.