If any country nuked another without a direct attack that couldn't be repelled through non-nuclear means as provocation it would be economic suicide - no country on Earth would continue to trade with them. They would have to pay crippling reparations. Sanctions would be put in place within hours. That alone is enough to stop any country using nuclear weapons in anger. The deterrent aspect of "mutually assured destruction" isn't really necessary any more.

A few years ago, that assumption would have been sound. After seeing it slightly tested in the past four years though... I don't think such an assumption really holds as an absolute certainty anymore.

We have seen developed nations continue trading with (and in some cases even increase their trade with) countries that have received international condemnation that should have seen unilateral embargos.

To name the first three that come to mind:

- Russia-Ukraine (land grab) - EU and Germany in particular increasing trade with Russia, particularly in terms of gas procurement when Russia should have been sanctioned into the ground

- Russia-Britain (killing on foreign soil) - same as above

- North Korea violating nuclear and ICBM testing treaty - most countries ceasing to trade openly, but continuing "off the books"

The US, murdering people with drones without due process and often by sloppiness and mistake. The land-grab in Guantanamo bay and some parts of middle-america. Supplying nuclear weapons to the likes of Erdogan and Merkel. Supporting an autocratic regime in Saudi-Arabia and a lot of other regions. Violating the Iranian nuke treaty unilaterally.

It's not US policy to use nukes to defend any country outside the declared US Nuclear Umbrella[1][2]; ie NATO Countries, South Korea, Japan and Australia.

The US (non-nuclear) defence policy on Taiwan is deliberately ambigious, and the US has no defense treaty (beyond arms sales) with Taiwan.

To quote Wikipedia[3]:

"The Taiwan Relations Act does not guarantee the USA will intervene militarily if the PRC attacks or invades Taiwan... America's policy has been called "strategic ambiguity" and it is designed to dissuade Taiwan from a unilateral declaration of independence, and to dissuade the PRC from unilaterally unifying Taiwan with the PRC."

[1] https://en.wikipedia.org/wiki/Nuclear_umbrella

[2] https://www.defense.gov/Explore/News/Article/Article/1822953...

[3] https://en.wikipedia.org/wiki/Taiwan_Relations_Act

FYI: Chen Shuibian has proclaimed independence like 10 times during his tenure, yet nobody even blinked.

This act is bull\w{4}, like many other defence treaties. The final word is always behind the executive power everywhere, and whether they have balls to go to war.

US nuking PRC for Taiwan does not sound possible. US won't even nuke the Soviets during cold wars.