As to China, Russia's beefs with China were always marginal (Russian Far East is not a very important part of the country), so no wonder China have no problem dealing with Russia. They have no major points of contention, while sharing a common enemy.

As per the geopolitical game in Europe between the US and Russia, the problem is that Russia wants eastern and central europe to again become their "sphere of influence", without any regard for what those countries want. Those countries know that being in US' sphere of influence means prosperity and peace for them, while being in Russian sphere of influence means poverty, political oppression, corruption, rule of stupidity, and potentially wars (forced to send recruits to help Russia). That's the major problem here - Russia wants to force on a bunch of its neighbors something they never said they wanted. In turn, they go to US for defence against their abusive neighbor. It's not US forcing itself onto Central and Eastern Europe, it's those countries practically begging to be protected (Poland's foreign minister was once recorded saying that "we'll suck America's dick for peanuts as usual", because that's Poland's only play).