There isn’t anything could do about the US invading Cuba because no one has much of a blue water navy outside the US itself.

Now granted, China is getting there but their navy is still mostly brown water (by design). And in any Taiwan / SCS conflict they would have an advantage because they can use their land assets, especially air force and land based anti ship rockets, on top of their navy.

The US land bases in the region are few or dependent on the grace of the host countries. Depending on political situation they might not Ok strikes against China if a conflict occurs for fear of being drawn into the war and angering China if the US loses. The only one Id be 100% on is Japan, they’d fight China to the last.

My gist is more no current bluewater Navy, including US is scaled to fight attrition battle in a near parity peer sized adversary's backyard. On paper this applies to current USN vs WestPac. Axis JP+DE during WW2, peak USSR were both ~1/2 of US comprehensive power, i.e. gdp ppp, % of global output, domestic industry output. PRC vs US closer to ~1-2x, with some metrics such as ship or munition building... order of magnitude more. In some gaps, US not even peak JP or USSR in relative terms. Even the month long 90s Iraq curbstomp required generational tech gab (french designers leaked/compromised IADs), 5 carriers and favourable regional basing (vs westpac), unsustainably high tempo sorties... when US militarily hasn't declined to current state in terms of capitalization... and Iraq then is charitably 1/100th the size of PRC. Unless there is unrevealed tech gap that still enables asymmetric curb stomp with a much smaller force - perhaps somehow none of Chinese hardware works, which at this point likely means completely dismantling PRC kill chain, i.e. what PRC intends to do vs US.

TLDR is the potential regional balance is increasingly lop sided in favour of PRC with gap widening, i.e. US+co can't preposition hardware at relevant rate. PRC hinted their cruise missile gigafactory has capacity to exhaust/target entire current US+co hardware inventory + stockpiles with few months production. A few more months enough to comprehensively shatter critical infra of US partners in 1IC. Hence why JP likely won't fight, because ultimately they're just a larger TW, also dependant on energy and calorie imports, and main islands also entirely within umbrella of PRC mainland fires. Mainland China is much better postured to operation Starvation JP than US from Marianas (25% further, and still needed logistics from CONUS) was during WW2. And if JP gives PRC excuse to fight them then PRC will (LBH be somewhat eager) to fight to the last JPnese. If JP doesn't, then they... well survive, maybe even still keep US protection. Most likely they'll only lose Senkaku when regional dynamics reconfigure. IMO current sign of JP not fighting is stronger than JP will fight... i.e. not opening main islands to distributed AGILE basing - US basically said they need JP in TW scenario, but they need to disperse all across JP not just Okinawa and Ryukyu's for survivability and JP action so far (since Trump1) is to not. It doesn't matter what JP politicians say for security theatre, IMO JP not committed until they start heavily militarizing main islands.