Russia is not weak. I agree but in terms of military numbers and geographic boarders they do have a real contested boarder. So how is it they are not weak?Talk about expansionist nations involves more than politics, may I suggest there is a universal principle at work, ie. high pressure will always tend to flow into low pressure. As China grows in population (now 3 children family size with funding from CCP), technology, economy, military, etc., this 'power' will flow into surrounding weaker areas. We see this power flowing to the east (Silk Road) to the south (India China border clashes), to the east, China Seas, Pacific Islands. We don't see it to the north because Russia is not weak. What America and its allies need to do is decide is the extent if any they will allow Chinese expansion into the Pacific area, and then create a power structure that will mitigate against this expansionist power without a war.
They are not weak because possibly China knows that if they open a front on Russia or even boarder creep Russia will respond with any and all available measures.
MADD can be used against a opponent. Keep the aggression or incursions low key but constant. You gain physical territory as well as psychological wins. Your opponent chooses not to respond because they fear escalation. Rinse and repeat.
thats is the history of Situation with Taiwan the SCS and North Korea for last. 30 years.
And no chinas expansionist ambitions are not a response to US policy. If that was the case why do the chines fishing fleets swarm into fisheries all over the pacific. Most recently the Galapagos maritime protection area.
They themselves have said they do not recognize the rulings of international bodies. They outright rejected the ruling for the Philippines over fisheries.