The peak for new cases in the USA has definitely occurred in the last month as can be seen here;-
https://www.worldometers.info/coronavirus/country/us/
but that page also shows you are right because although deaths have risen in the last few weeks, the peak for them definitely occurred during the "first wave" which was based around New York back in March/April and I'd say that the figures would be showing a sign by of climbing to April levels by now if they were going to do so.
While it takes a level of expertise beyond us on here to make a convincing case that this apparent dilution of the virus' ability to kill humans is down to it mutating into something less lethal (I'm unaware of any study saying this is the case anyway), I'd say that, certainly, in westernised countries that are experiencing a resurgence of cases, there is quite a bit of evidence out there that the more likely Covid sufferer this time around is younger than your typical victim in the late winter/spring, so that should equate to less deaths.
I'd also say that there are a few treatments proven to be effective against fighting the virus out there now which were not recognised as such a few months ago, so I'd say there are two reasons which are backed by research which confirms the suppositions behind them, so I'd say they are more likely causes for the lower number of deaths than a mutation to something less powerful in the virus.