Obviously a narrow strait like this would be easy to blockade.
However I would draw attention to the tanker driver strike in the UK
a few years back.
In three days the supermarkets were virtually stripped bare.

It would probably take a week or two before service stations were
affected and then another week before food ran short, then a couple of
weeks before starvation set in.
Once people realised the implications those timescales would be shortened.

How long after that before Iran was a sheet of glass ?

It is not a realistic tatic for Iran.

Of course, the issue arises only because of Iran's pursuit of nuclear weapons and Irani statements suggesting that they would be used on Israel. Those issues can not be resolved via discussions with the IAEA, they can be resolved only by Iran genuinely renouncing nuclear weapons and dismantling all nuclear weapon-related facilities under international supervision. The ball is in Iran's court, not those of the IAEA or international community.

Despite Iran having forsworn nuclear weapons and opened their nuclear program to an unprecedented level of international inspection, they are still being accused of having a nuclear weapons program. This accusation has been growing in volume ever since the UN's IAEA gained a US and Israel friendly head.
Perhaps Iran is building something in secret. Can they be blamed in light of what happened in Libya and Iraq and didn't happen in Korea?
Israel is one of the loudest voices calling for an attack on Iran, all the while repeating a misquote attributed to the Iranian president. He is not the only one thinking that the Zionist regime in Israel/Palestine is up to no good. Nor is he the only one thinking Israel would gain credibility if she were to open her nuclear program to international inspection to the same level she demands of others.
A possibility seldom if ever considered is that Iran and the "west" are natural allies. We're a match made in heaven, if only the fishwives would let it happen.

Iran can't block the Straits of Hormuz, for if it did, that would
be seen as trying to blackmail the rest of the world. Iran as a
result, would get what it deserved, through every fault of its own.

More likely, as the locals in Iran are restless and would like to
overthrow the Govt, which hangs on by every means of corruption
it can think of, the Govt needs an outside threat to try and rally
local support behind it.

With the Straits of Hormuz it would have picked the wrong way to
do so, for them remaining open is far more important globally
then the present Iran regime.

So block the Straits at your peril and the result won't be pretty.

Halduell;
Had it occurred to you that Iran might have let the IAEA
inspect all sorts of places, but not told them of other places ?

In fact, that is just what the IAEA reported and what has lead to the
current unease. They are not so naive to have come to their conclusion
without some evidence.
They study such things as material ordering and production of fuel.

The number of centrifuges was one clue that they mentioned.

Let recent history guide us.
The US invaded Iraq because it thought Iraq had ‘weapons of mass destruction’. It found none. The US did not then leave, it stayed for some other motivation.
Prior to the invasion of Iraq, the US initiated a huge PR campaign trying to prove there were weapons of mass destruction. When that media campaign was complete they invaded.

We now see the same propaganda campaign against Iraq and it will likely lead to an invasion of Iran if a desperate US sees it as a viable option. In addition to oil, perhaps the state of the US economy will provide a further motive to invade, in that people unite behind their governments in times of war.

On the qualities of the governments in both countries; the US through its corruption of the financial system is shown to be a most destructive agent. Its invasion of country after country over many years also proves it is a warlike country. How can the quality of Iran government be a justification to attacking Iran