Many things about the US are far to the left of most countries. For example, birthright citizenship.
Since when is the constitution leftist? Birthright citizenship isn’t a left or right question at all in Europe. It’s not a thing there. Neither left nor right wants it.
Pretty much the entire “New World” has birthright citizenship, so it’s not just the US thing and I don’t believe its origins are political at all.
The US has always been a nation of immigrants, but now its largely a nation of ignorance.