Not that you’re wrong, and not that I disagree with much, but I would take issue with your cherry picking.
The United States is a Federation. The States do have strong borders, their own laws, their own takes on a republican system, even their own electoral and judicial systems that are in many ways distinctly different. California is not distinct from South Dakota in this way.
The States do tend to have very large GSP’s relative to most countries, always directly comparable to the GDP of a nation. This is two parts being part of the single largest national economy in the world and one part the fact there are some very poor countries in the world, and even some European countries aren’t exactly rich, even if they aren’t exactly poor either. Generally each State does punch above its economic weight, even if the budgetary considerations are often complicated by that largest national economy in the world having a multi-trillion national budget backing up four of the largest armed forces in the world.
However, that doesn’t make each and every State particularly relevant to an internationally-minded person of the world. A well educated person might be able to name every nation in Europe, South America, North America and even the Middle East and quite a number of subdivisions to boot, but what about Micronesia, Africa or Polynesia? Most probably won’t be able to tell the difference between Polynesia or Micronesia anymore than they can tell the difference between North Dakota, Alabama or Colorado.
Then certain other States have brands, and punch way above their weight. California. Texas. New York. If they are well known, it is because they are distinctly relevant on the global stage by themselves. California alone has Hollywood, Silicon Valley, San Francisco, Stanford and Wine Country. These are all fairly well known brands on their own, SFO and LAX are effectively brands to a well seasoned air traveler.
The fact that California has an economy in the Top 5 in the world in her own has no bearing on the life of your average adult almost anywhere in the world, but they will probably recognize the products and services of California, Inc. Even if they don’t, there is still a decent chance they partake in some of California’s bounty of farm products, almonds in particular are largely grown here.
My point being you can’t cherry pick California and use an argument that would apply to any of the other 50 States when you can also make many of the same claims for: German States, Austrian States, Swiss Cantons, Australian States, Canadian Provinces, and UAE Emirates (name more than two without looking it up, you might be able to but at most the only two most hear about are Dubai and Abu Dhabi), and these are just off the top of my head.
There are a lot of places that get to make their own laws and enforce them. In the United States there are many tribal nations that get to make their own laws and enforce them which are largely anonymous and unknown to most Americans and you won’t find them on most maps that mark the States. That doesn’t necessarily put them all on the same level as the sovereign countries they reside in. Norway is a sovereign country, California is not. The United States is a sovereign country, the European Union is a mess of treaties.