When soldiers are told to fight or else they won't get paid and they will go to prison, that is a strong motivator for fighting... In fact most of them won't even need to be told those things, they will understand those issues...
When the threat of a real war materialised in 1990 there were a lot of soldiers who tried to find reasons not to go... in fact I remember there was one ship that got the nickname "The Love Boat" because so many women on board suddenly got pregnant that it was so under manned that it had to delay going to war while replacements were sorted out...
Obviously getting pregnant is not an option for men, but there are always plenty who wont want to go to real war where there is a serious risk they could be killed or injured and a conflict with Russia would count as a conflict where the risk was rather high IMHO.
Of course many will be keen to fight because they know with all superior weapons and equipment being American made they will win. Lots of others however will not be so confident... they will be called whistle blowers or cowards at best and traitors or terrorists at worst... and I rather suspect there will be quite a few of those too.