American ambiguity towards the protection of Taiwan was, in its initial phases, just a diplomatic formula. There was never any doubt about our willingness or ability to fend off a Chinese attack at the time. Our military predominance was obvious to both sides.
That is no longer true, at least for what the Chinese would view as a home game. There is some talk of creating a red line in order to avoid stumbling into war over the issue. That sounds like Obama’s line in the sand on Syria to me. It’s a bad idea.
The Chinese are going to make their decisions based on what they see, not what we say. Making an unequivocal commitment to Taiwan would sound more like weakness than strength to them. If Biden is wise, he will maintain the status quo, and back it up with actions rather than words.