Or what if the United States withdraws its unwavering support for Taiwan in the same way that it is withdrawing its backing for Israel to strike Iran?
Yes, in the 2030s, I see the US withdrawing support for Taiwan.
In the past 3 years, we've already seen the US and Japan walk back statements that in the event of a Taiwan-China conflict, they have the option of going to war with China.
That leaves potential economic sanctions, which are still enough of a deterrent given that China can live with the status quo and doesn't want a war which will inevitably district from domestic development. In the longer-term, that economic development will translates into much greater military capability and political/economic influence anyway.
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Just going back to the topic of Israel.
Suppose China were to formally recognise a Palestinian state? I reckon most of the world would support this. For example:
1. The Australian government is formally floating this idea in the press
2. Spain is pushing for this as well. And inside the EU, you've got Spain, Belgium, Ireland and Slovakia pushing against Germany, Austria, Hungary etc. And remember the view outside of the West is generally far more pro-Palestine
3. In a prior UN resolution over Israeli colonists trying to take over the West Bank, it was literally every single country in the world voting against Israel, with the sole exception of the USA
4. Even in the US, 55% of Americans disapprove of Israel's actions in Gaza
It should be clear that decades of Israeli military occupation of Gaza and the West Bank haven't worked, and that the conflicts on Israel's borders will not stop until either the Palestinians have their own state or the Palestinians are full citizens of Israel.
Given that there would be more Palestinians than Jews in such a Greater Israel, a democratic Israel would cease being a Jewish State. The alternative is full-on apartheid in Israel which isn't going to work either.
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So if China (and others) were to recognise a Palestinian state (at least in the West Bank), what would happen?
The Palestinians could demand the removal of the Israeli Army and 500,000 Jewish colonists from the West Bank. My guess is that Israel would resist the removal of its colonists, as Israeli society has taken a sharp turn towards the conservative, religious right over the past 2 decades. Plus the demographic and political trends are for Israel to become even more so in the future.
At a minimum, these Israeli Army bases supporting those Jewish colonists in the West Bank become valid targets.
Rationally, it is not in US interests to be dragged down by supporting such Israeli actions and siding with the bad guys. But my guess is that the Israel Lobby would still be powerful enough to convince US politicians into supporting Israel's colonial oppression of Palestine.