Who in the US said?
Methinks this is either Ukrainian or Washington propaganda.
US Says? We didn’t say squat.
True, it is warming up a bit now, but there have been some periods below freezing even in the daytime hours across most of the conflict zone in the past two weeks. So if in fact there are Russian forces without adequate cold weather gear then they could in theory have suffered frostbite.
In general terms, it seems to me that Russia is more analogous to Fascist Italy than Nazi Germany, in having a large military force that is not quite up to the same level as some of its smaller opposition, at least in terms of organization. However, if a large mediocre military takes on a smaller excellent one, at some point the sheer superiority of numbers will determine the outcome.
My comments are not meant as an endorsement of the conclusions drawn, just to address the question of whether or not it ever was cold enough for frostbite, and most locations in Ukraine have seen some overnight temperatures in the 15-20 F range and some daytime readings in the high 20s to near 32 F. There has not been very much snow during this cold weather, some places avoided it altogether, and others had small amounts of about 1-2 inches. That has been visible in some video of the conflict, and any traces of it are probably already gone. These milder temperatures at the present time will be turning partially frozen soft ground more muddy even if it doesn’t rain, and especially if subjected to heavy vehicle traffic.
I had a look at the latest weather guidance and it appears that this milder, dry weather will last about a week to ten days with some minor fluctuations where it cools down into the high 30s (F) around this coming weekend, then back up to current levels, but it should stay relatively dry for about two weeks before a much wetter interval develops with temperatures in the 40s and 50s F. If there is still fighting then, it could become very muddy in that time frame (roughly April 1-10).