Cold waves in Eastern USA are down according to Dr Roy Spencer.
As can be seen in the plot below, there is no evidence in the data supporting the claim that decreasing Arctic sea ice in recent decades is causing more frequent displacement of cold winter air masses into the eastern U.S., at least through the winter of 2017-18:
The trend is markedly downward in the most recent 40 years (since 1979) which is the earliest we have reliable measurements of Arctic sea ice from satellite microwave radiometers (my specialty).
Now, I suppose that Arctic sea ice decline could have some influence. But weather is immensely complex. Cause and effect is often difficult to ascertain.
At a minimum we should demand good observational support for any specific claim. In this case I would say that the connection between Eastern U.S. cold waves and Arctic sea ice is speculative, at best.
Just like most theories of climate change.