You haven’t probably noticed, but the United States HAS slightly changed its name, so to speak. Some countries change their names over the course of time, but the way the US has done it is very different.
We say different because the change is so subtle that is barely noticeable. Before the Lincoln administration, they were the “United States.” After Lincoln, it was the “United States.” Can you spot the difference?
Of course, no! You can’t see the difference because it’s not a change in words or spelling. The change is purely grammatical. Before, people said “The United States are…” Now, people say “The United States is…” The idea was to draw us away from that original idea of independent states forming a voluntary union, and to the idea that this was one nation of provinces, called “states.” A collection of states forming one whole.
Now, no one sees The United States as plural, even though it is still spelled as a plural. Everyone treats it as singular, and that’s the difference grammar makes.
This was summed up in a quote by Shelby Foote that goes along these lines:
Before the war, it was said ‘the United States are’ – grammatically it was spoken that way and thought of as a collection of independent states. And after the war it was always ‘the United States is’, as we say today without being self-conscious at all. And that sums up what the war accomplished. It made us an ‘is’. _Shelby Foote