I got into trouble in the States, because of this ignorance. Stopped at a bank to draw some cash. Teller said “I know where you’re from! You’re Canadian”. Said no I’m not, I’m English. She said “One moment”. 5 minutes later, officer, hand hovering over gun, asks why a “britisher” has a Canadian credit card. I said “First, there is no such thing as ‘Britisher’, thank you.”
Then I explained that Halifax was a fine city in the north of England. Been there for hundreds of years. Yes, longer than that new place in Nova Scotia. Yes, it was a Halifax card. I don’t think they believed me until a local guy stepped in, telling them that’s where his “folks” came from.
I once had a minor disagreement with someone from Texas. This took place in the US (obviously). He remarked on how well I spoke English. I said, “well I’m from England so it’s hardly surprising”. He gave me a blank look, evidently not understanding my point. I added “you see the language, ‘English’ was named after the country, ‘England’”. He looked at me in a way that I interpreted as a mixture between confusion and pity, before replying “no, you named your country after our language”. He was completely serious.
Edit: disabling comments. Too many people are writing answers to the question in the comments field of my answer.
This is Boston, Lincolnshire, UK.

Every single building in this picture predates the USA including the Tower in the background which was uilt in the 12th century, that is the 1100s, more than 300 years before Christopher Columbus was even born.
This is Dover Castle, close to the town of Dover, UK.

It was founded by the Romans only a couple of decades after Jesus walked the planet. It is nearly 2,000 years old. Most of what you can see is about 950 years old. It was still in use as a military base during WWII.
This is Birmingham:

The canal you see was dug a year before the George Washington became the first POTUS.
This is The Shambles in York, the city New York was named after.

None of the buildings you see are less than 500 years old. This is not Disneyland, they weren’t built to look old, they are OLD!!! What’s more, they are not museums, they are actual shops and homes. People actually live in buildings this old all over the UK and think nothing of it.
My friend lives in a cottage that dates back to 1233, 543 years (that more than half a millenium) before the Declaration of Independence. When George Washington became President, my friend’s home was already nearly twice as old as the USA is now. In fact when Christopher Columbus discovered the new world, my friend’s home was older than the US is now.