Nothing against Prime Ministers as head of states. In fact I prefer most aspects of the parliamentary system to what the US has.

The link to wikipedia I gave also lists other heads of state like prime minister and so on.

But why I picked Argentina. No reason besides words have meaning in their origin of language, and not just in the descriptive state we use them to describe objects. President and Prime Minister are different words in both how they describe the object but also where they came from.

Now understand what you call your head of state like President, Prime Minister, is arbitrary and why one country calls their A thing X, and another country B calls their thing Y can often be due to silly things, or imaginary distinctions, but language matters for language is how you communicate and very few people outside of Japan know what Nippon is or Nihon for in English we normally use the word Japan which is the British name of what they called the land of Japan, and not what the native Japanese called their land in their mother tongue. So when speaking about Japan in English you will see more uses of the word Japan, but why Japan instead of Nippon...you can list dozens of reasons why A or B but in the end you switch from logical rationale to what everyone communicates due to effectiveness.

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Oh side note I personally prefer the term Prime Minister, for I think government should serve the people so a word that means literally in latin, the first server / first attender and this title for head of state is more romantic and sentimental to me than president which means in latin to lord over, or leader. But that is me being sentimental