Actually looking at it afresh, its not difficult after all to track the path from here to the US declaring an Embargo
Step 1) Realisation that US will not defend any declaration of Independence or try any meaningful measures to stop a PRC military re-occupation on the Island, leads to the fall of the DPP Government
Step 2) Newly elected KMT government start making serious moves towards re-unification
Step 3) US disputes the election results and accuses China of interfering in Taiwan's democratic process
Step 4) US declares part or full embargo against China (to include Taiwan under KMT)
(actual scale of embargo may depend on how far the reunification process goes, as the US will want to keep plenty in hand for escalation purposes).
I think you are way over estimating the vision, will and balls of Washington politicians to have dreamed up such an elaborate plan; or to get onboard such a plan someone else developed and presented to them.
I think you are also vastly overestimating the need for a narrative or reason in the decision making process in western capitals.
My personal view is that the only thing that western leaders truly consider when making decisions on foreign policy in general and military intervention in particular can be safely distilled into a basic cost benefit analysis.
With the control of the western MSM, the pretext has never been the issue. If western politicians want a war, can the easily manufacture the pretext.
The benefits part are broadly along national interest lines, but only insofar as what can be easily and readily converted into political capital and and domestic votes.
The costs are in terms of soldiers lives that might be lost.
The current American strategic realignment is the military response to current political realities.
Simply put, the generals at the pentagon has concluded that the cost in American lives of fighting China in and around Taiwan is almost certainly going to vastly exceed any possible benefit said politicians can possible even hope to gain from the fight (the fact that America is almost certainly going to loose such a fight is pretty much relegated to the fringes of western discourse and would never be allowed to be spoken of openly in western halls of power). And that despite what they are saying now on soap boxes, if the balloon goes go up for real, they will almost certainly blink and back down.
Thus the military is shifting the battlefield from China’s front door to the Indian Ocean to try to rebalance their expected looses to get back to within the realm of being politically acceptable.
The grand game plan is to start a fight with China in the Indian Ocean to deprive China of its home field advantages, destroy the PLAN in the Indian Ocean. And that will then unlock all of the previous military options available to America which China’s military modernisation has nodeprived it of.
Once the PLAN is out of the equation, China’s SCS islands will no longer be the tip of the spear, but a cut off collection of outposts. That opens the door for effective blockade of Chinese sea based trade without killed off world trade as collateral damage. Beyond that military occupation of Taiwan might even become an option.
This all hinges on drawing the PLAN main strength into the Indian Ocean so it can be cut off and destroy there. This is also where Australia’s nuclear sub deal start to make sense as they can use nazi U-boat tactics against China.
I would also expect significant work being done to get India ‘on side’ as I think that is going to be the fulcrum on which this American plan will turn.
Rather than fight China directly, which will never work as China won’t take the bait. They will build up India and have them start the fight with China. With Australia helping covertly with their SSNs.
It is hoped that China would be prepared to send the PLAN main strength into the Indian Ocean to punish India, after which the US and invent a pretext to get involved and ambush the PLAN in the Indian Ocean to materially weaken the PLAN enough for all of the above to be viable.
The 20-30 year timeframe is probably to allow America to gain enough influence over India to act so drastically against its own national interest; to build up the Indian navy sufficiently to require enough of the PLAN to be committed for this all to work. In addition, in 20-30 years, the BRI will also have grown exponentially compared to now, making it more likely that China would be forced to fully respond to any Indian direct attacks against core elements of it.