Taiwan has a good friend with nukes though.

Most countries have good friends with nukes. Iran included.

Does Iran have friends or are they more like business relationships?

Even despite Trump, I think the US and many western countries have actual friends that would show up if bad things happened.

The US isn't nuking China over Taiwan, and China maintains an explicit "no first use" policy.

TSMC is an economic nuke and not just by accident. The Taiwanese intentionally tried with several industries it heavily subsidized to find one where it could make itself so valuable that other countries (with nukes) would be compelled to protect it (potentially with nukes).

I don't expect this to stay true for very long :(