"I don't understand why the US is one of the few remaining first-world nations not to offer universal health care."

I understand it. It goes back to the founding of the nation. This country was founded by people who, for the most part, saw government as oppressive. Their default mode was the less of it, the better. You see that  reflected in the U.S. Constitution. The lion's share of that document focuses not on the capabilities of government but on the limitations of it.

That mindset has lingered throughout our history and it's a tough nut to crack.  The problem is, the founders never envisioned a nation of 300+ million with an average life expectancy into the 70s and 80s. Today we seriously need to think of universal health care as an essential human right, not a luxury for only those who can afford it. 

BTW, I gave your post a "like," Monica, but please don't interpret that as suggesting I want you to move back to Italy. 😊