whereas Iran has nowhere near the reach required to do likewise to the United States.
The US would be able to deploy and rotate assets on/off Diego Garcia, and while they might not be able to muster as much firepower per unit time as the Chinese could onto Taiwan, the US has the tyranny of distance on their side. The Iranian missile and fighter forces would not be able to strike back. As the conflict progresses, US air and naval forces would be increasingly efficient at eroding Iranian counterattack capabilities while suffering little to no risk of reprisals. Moreover, the US operation does not require landing boots on Iranian soil, which makes such an undertaking much less complicated than a Taiwan scenario.
So you are absolutely right that nobody should be equating Taiwan with Iran; the former would be a much more complicated and potent adversary to deal with, and if the USN already has trouble fighting Iran given all the profound advantages, then the PLAN would do well not to fight a war with Taiwan.
Iran dwarfs Taiwan in power? China's military is rivalling that of the US?
Once we are back in reality, let's take a look at the numbers.
The IRIAF has some ~300 combat aircraft, of which ~30-40 are the somewhat-modernized F-14. The operative term is "somewhat". The rest of their inventory could be dismissed as obsolete 3rd-generation airframes that wouldn't be of much relevance in a modern war.
The ROCAF has around ~400 combat aircraft, of which ~200 are the F-16V standard uprades & newbuilds. This is almost comparable to the PLAAF's entire J-10C fleet in terms of both quantity and capability. In addition to that, the rest of their fleet are comprised of the F-CK-1 and Mirage 2000, both of which are of the 4th generation and likely more capable than any of Iran's fighters.
Let's not forget about the ROCAF's force multipliers such as its E-2 fleet. Let's not forget that - while Iran has certainly shown its mettle with its array of ballistic weaponry - Taiwan has a large stockpile of long-range supersonic-capable cruise missiles. This is not to mention naval forces.
I see the tyranny of distance as an advange for the US; Diego Garcia is almost 5000 km from Iran - US jets could hit Iran and the latter would not be able to retaliate unless it's against some other US base in the region.