The strait is 34 miles wide at its narrowest point. Its legal status is functionally as international waters, due to the right of innocent passage described in the 1982 Law of the Sea treaty. Iran disputes this, but the whole issue is seriously muddled because some countries have signed the treaty but not ratified it, we haven't signed it. Iran wants to say innocent passage only applies to those who have ratified the treaty, but they don't have any serious international support.
Meanwhile, an average of 13 loaded oil tankers transit through the strait every day, and there are numerous naval assets in the area, not just the US Navy, determined to see that the strait stays open.
If Iran would attempt to block the strait it would rapidly lose its navy and regret its impulsiveness.
They intend to escalate a bit more,,,,see link at # 21.