It's not an influenza virus.

That said, even if it was, a "very strong flu" with global transmission and impact _is_ a pandemic -- see the 1918 Flu Pandemic.

The death rate in 2020 in the US also surpassed that during the 1918 pandemic.

What I think we've learned is that the same measures used to slow the spread of COVID-19 are staggeringly effective against the flu, and that we now know how to prepare for the next particularly aggressive influenza variant.