One reason why the US sits pretty and attacks at the slightest provocation and Russia needs to be pushed is rather simple.
The US is safe from anyone who would oppose them and any war has no chance of ever coming back to the USA. As well the USA isn't really responsible for anyone either, their direct actions do not hurt anyone they care about indirectly.
While Russia is surrounded by enemies who can walk over, they have several nations between them and other enemies who would be in the crossfire as well.
Basically the US has no vested interest in peacekeeping so to speak.
Ok to put it in simpler terms, your analysis is completely wrong. The US makes a huge fuss over their soldiers getting killed because to not do so would be political suicide domestically. The effects on 'anyone they care about' (I actually have no idea what you're referring to here, so I'll assume it to be other nations in this context) also have a huge impact on their response to provocation, insofar as the US military covers a lot of allied nations' defence needs, and they can't afford to look weak. The point about North Korea is that the US is completely capable of rolling over them in less than a week and with zero damage to the continental US, but also causing unacceptable (literal?) fallout to South Korea and Japan, so in this case the effects on other nations are being considered into US decision-making. You will note that North Korea has done a hell of a lot more provoking than the Syrian government has, with near-zero military repercussions from the US.
Oh, and the US first confirmed North Korea's possession of nuclear weapons in 2009.
In contrast, Russia has basically no domestic politics to speak of, so there's no internal pressure to save face other than to the international community. They (by which I mean Putin) can afford to wait and not respond to provocation (see Turkish military shooting down a Russian fighter with explicitly hostile intent) if doing so would not be in their favour in the long term. I again have no idea what you mean when you say 'enemies who can walk over', but the second part of your sentence there is also false. You're implying that the only reason Russia won't start a war with the US is out of concern for all the poor Eastern Europeans in the way, and anyway Russia's current geopolitical rivals, with the exception of the US, all share a land border with them or their satellite states.
Ohh but you forget the part I didn't put in
Neo, I think that quote showcase the difficulty of discussing with you in a nutshell.
This. Silly me for not reading your mind and responding to arguments you haven't written!