Something hasn't been done yet doesn't mean it won't happen. Everything is they haven't already done it before they actually do it. What has already happened is the US deployed THAAD in S. Korea, slapped a bunch of sanctions on China, created the Quad, and then now forming US-UK-Australia arms pact. So don't be complacent. If China's inaction continues, the US and its minions (Taiwan, Australia, Japan, Canada, UK, S. Korea etc) will do those things step by step.
I'm sure they're willing to pay any price to destroy China. The price doesn't matter as long as you win the war and get rid of your enemy. Once your enemy is gone, it's all yours and you can recover. Paying a hefty price and be the sole ruler is better than not paying any price and have your enemy as a risk. That's how wars work and why humans start wars. You need to be willing to pay whatever price to dominate to survive in this 'either eat them or get eaten' jungle.
Taiwan, S.Korea, Australia are already deploying missiles, submarines and submarine-launched missiles to target China. The US has been actively arming its minions around China and China has border conflicts with India as well. China doesn't have much time left. Taiwan and S.Korea need to be sorted out for a first step at least within 1-2 years. If China wastes more time, even those small countries around China will soon be impregnable and will be aiming right at centers of China.
Look at it this way.
What you are talking about is warfare.
With the Chinese Communist Party and Chairman Mao Zedong, warfare means all the ancient Chinese texts like Sun Tzu and modern texts like Carl von Clausewitz.
Clausewitz had this concept of the "Center of Gravity," which is the source for the strength of the enemy.
This could be a supply depot behind the front lines, or tank column. It could be anything. Where is the source of the enemy's true source of power and our side should try to eliminate that.
Chairman Mao really like Clausewitz a lot.
What the United States has done, does not hit any Center of Gravity against the Chinese.
Also, any attempts to hit the Center of Gravity of the Chinese have proved to be futile or very limited in its intended effects, aka, it failed.
It is no secret that the Center of Gravity for China is the Chinese economy, and it integration into the world supply chains, and the economic relations that result from that.
To suggest that America and Korea will work against Chinese and Korean interests, meaning Korea will work against itself, that is pure propaganda.
I'll prove it. Give me $10 bucks right now! Where's my $10 bucks? How come you did not give me the $10 bucks I asked for?
Now, these new subs from Australia, does nothing.
If we cannot identify the enemy's Center of Gravity, and then attack the wrong or a fake Center of Gravity, well then, we know who is going to lose the war.
How does these new subs 10-20 years later stop the Chinese economy and RCEP from doubling their economic output in 10-15 years. That is what China wants.
The United States has done nothing to get in the way of those Chinese economic goals.
The United States has been unable to prevent China from getting what it wants in almost all issues.
To try is one thing. To try and fail is another thing. To try and fail, that accomplished nothing.
The United States has done nothing in almost all issues to stop China.