A blockade is an act of war, carried out by military force. Saying the US is blockading Cuba is saying that the US and Cuba are at war. That alone is a pretty big reason to understand the difference between a blockade and an embargo.

The other important dimension is that countries participating in the embargo are choosing to participate in the embargo. This is distinct from a blockade which is done unilaterally. The Royal Navy didn't let ships into Germany ports during WW1 if they paid a tariff. No, they seized ships bound for Germany, because that was an actual blockade.

An embargo is when countries decline to trade with you on their own accord.

A blockade is when a country uses military force to physically stop other countries from trading with you, even if those other countries want to trade with you.

They're pretty substantially different.

The US won’t even admit to being at war with Iran, and more explicit acts of war have clearly been committed there.

An act of war also isn’t the same as being in one. It takes two to tango, to some extent. Many acts of war do not result in one.

Act of war, no war: https://www.cnn.com/2002/WORLD/europe/02/18/britain.marines/...

Is the meaningful thing you are trying to get across here something like: "everyone is saying USA is doing something really bad, but in fact they are not"?

Or maybe more: "ok USA might have it a little out for Cuba, but remember, everyone else hates them too, otherwise they would be trading with them"?