Go from Wales, Alaska near the Bering Strait to the southern tip of Florida. You have traveled 4,580 miles (7,370 km) in 14 states and provinces. At no point were you not in a jurisdiction that was predominantly English speaking.
Mandarin Chinese may have the most number of native speakers, but English has the most number of total speakers, and those speakers are spread much more widely around the world.
The US is a business, economic, and geopolitical powerhouse. So was the British Empire.
I’m not saying that every other language should crawl in a hole and die. I’m currently taking a crack at learning Spanish. But there are pretty solid reasons why Americans make assumptions, even if they are erroneous sometimes.
It looks like the type of visas that are usually used for vacations give you 180 days per stay and last for 10 years. From what I’ve heard, they’re either fairly easy to get a hold of or ridiculously hard depending on your country of origin. In other news, everything in the US around visas and immigration is fuuuuuuccccckkkkked.