We do have the Taiwan Relations Act but it's not a treaty. It only requires sales of necessary military equipment. It doesn't require the US to defend Taiwan against China. The US probably would mount some kind of defense against an invasion but ultimately it's up to the President.
The Russian Federation, the United Kingdom of Great Britain and Northern Ireland, and The United States of America reaffirm their commitment to Ukraine, in accordance with the principles of the CSCE Final Act, to respect the independence and sovereignty and the existing borders of Ukraine.
The Russian Federation, the United Kingdom of Great Britain and Northern Ireland, and The United States of America reaffirm their obligation to refrain from the threat or use of force against the territorial integrity or political independence of Ukraine, and that none of their weapons will ever be used against Ukraine except in self-defense or otherwise in accordance with the Charter of the United Nations.
The Russian Federation, the United Kingdom of Great Britain and Northern Ireland, and The United States of America reaffirm their commitment to Ukraine, in accordance with the Principles of the CSCE Final Act, to refrain from economic coercion designed to subordinate to their own interest the exercise by Ukraine of the rights inherent in its sovereignty and thus to secure advantages of any kind.
The Russian Federation, the United Kingdom of Great Britain and Northern Ireland, and The United States of America reaffirm their commitment to seek immediate United Nations Security Council action to provide assistance to Ukraine, as a non-nuclear-weapon state party to the Treaty on the Non-Proliferation of Nuclear Weapons, if Ukraine should become a victim of an act of aggression or an object of a threat of aggression in which nuclear weapons are used.
The Russian Federation, the United Kingdom of Great Britain and Northern Ireland, and The United States of America reaffirm, in the case of Ukraine, their commitment not to use nuclear weapons against any non-nuclear-weapon state party to the Treaty on the Non-Proliferation of Nuclear Weapons, except in the case of an attack on themselves, their territories or dependent territories, their armed forces, or their allies, by such a state in association or alliance with a nuclear weapon state.
Ukraine, The Russian Federation, the United Kingdom of Great Britain and Northern Ireland, and The United States of America will consult in the event a situation arises which raises a question concerning these commitments.
Edit - Russia is in breach for failing to respect Ukrainian sovereignty. The US and UK are not in breach for failing to send troops. The EU (nor any other member states) wasn't a signatory, so it doesn't apply to them at all.
You’re right though, it doesn’t spell out any mutual defense statements.
It was a strategic ambiguous treaty, so the "obligation" ranges from an US general raise eyebrow or nuke China.
But regardless of the truth (or usefulness of his statement), I am almost certain that he would not extend that to NATO's naval response. Firstly, since NATO straight up said that it's not going to engage Russia in Ukraine, it's not clear what NATO naval forces in the Black Sea would do other than increase the risk of escalation. Second, as the article points out, NATO has to deal with Turkey - a situation that the US does not quite have in the western Pacific (though exactly how supportive South Korea and Japan would be in the case of a Taiwan invasion is a bit of an unknown).
Also, there is nothing that NATO can do to stop Russian Naval deployments into the Black Sea. Asking Turkey to close the straits would a) almost certainly be refused, b) be an incredibly bad look for the side that performs freedom of navigation missions into the south china sea and c) cause a shit load of kerfuffle as the split between Turkey and the rest of NATO gets forced to the surface in an awkward manner.
Finally, we can look at the US Navy's current deployment of major assets - https://news.usni.org/2022/02/24/usni-news-fleet-and-marine-...
There's a carrier strike group deployed in the Mediterranean, and one in the western Pacific. There's a forward deployed carrier in Japan. As the article notes, there's also an French and Italian carrier group deployed into the Mediterranean. There is plenty of "real" naval strength nearby.
If the US were to engage in Ukraine, Taiwan would be up for pickings. I believe it would be a mistake. The US doesn't have the dynamism it once had, it's population in large part isn't fit for combat, or resilient to casualties, and is preoccupied with internal striffe. Defense budgets are high but what a US DoD buys with 1$ is a lot less than what China buys with the same value, since US defense industry is bloated and burning through budgets. All this to say, the US can't sustain two flanks against two strong foes, it needs to pick its focus and China is the real strategic opponent.
I hope this international environment will wake up the US public and industry, and that this will all end better. I also hope that Germany will stop using so much gas and being a pawn to Russia, and that the EU will take care if their defense more, as the US isn't in a position to do like it did during the Cold War.
Now, if Taiwan were to apply for NATO membership, I would expect the Chinese response to be much more swift than Russia's.
"NATO’s naval response to Russia also has implications for the West's ability to assert its interests elsewhere, such as the South China Sea, where Beijing claims sovereignty.
"If, with the whole world watching, we cannot deter the Kremlin, I don't think the Chinese will be terribly impressed about what we say about Taiwan or the South China Sea," said retired U.S. General Ben Hodges, who commanded U.S. Army forces in Europe from 2014 until 2017 and who met Ukraine's President Volodymyr Zelenskiy in Kyiv in early February."