You’re right. The population in 1957 (172M) is roughly half of what it is today (331M). And you’re also right that this would equate to roughly 230,000 deaths today - I calculated 223,240.
What you’re missing, however, is the fact that we will never have another death from the 1957 flu pandemic. We will continue to have deaths from the 2020 COVID-19 pandemic. We’re averaging roughly 1,000 deaths a day. At that rate (and I see nothing that says the fatality rate will change in the next two months), we will surpass the fatality rate from 1957 by sometime in mid-October.
The America of 1957 was run by the refd-blooded veterans who won World War II. The America of 2020 is run by snowflakes.