Earlier quoted context omitted.
And that's recorded cases. There might be people who died from Covid-19 who weren't tested post-mortem, especially in February when the virus was flying under the radar. NYTimes had an article which showed a number of places around the world have had a surge in deaths compared to the same time period in previous years. And even if you subtract the known Covid-19 cases, there's still a sharp increase in the count.
That's the exact opposite of what's happened. The number of deaths being reported includes "probable deaths". It's even more than the actual confirmed cases. Look at the graph on the last page for NYC for example: https://www1.nyc.gov/assets/doh/downloads/pdf/imm/covid-19-d...
Just because they are counting probable deaths does not mean they aren't also undercounting the true deaths. Given the rate of testing confirmed is clearly Excess death data so far suggests that they are indeed undercounting true deaths. While it is certainly possible lockdown has caused some additional immediate deaths, it is also likely other deaths (eg decreased car accidents) have gone down. So it will require further analysis once this is all said and done and more data is available, but my money is that the US has undercounted deaths thus far.