Many americans seem unaware of many things that happened before 1776. How many americans even know that the constitution wasn't made until many years later, how many even know the articles of confederation exist, or the politics of 1600s colonies? Many americans seem to think the declaration of independence is legally binding.

We are an incredibly stupid country, because many of us actively devalue education, or otherwise denigrate people who learn. The requirements for teaching and education varies wildly state to state, including many states that basically have NO requirements for teachers, and we have actual, real, paper textbooks purchased by southern school systems that teach slavery as "not that bad"

The US mile is different from the UK mile and US gallons are sufficiently different from UK gallons. Yes, our measurement system is almost entirely homegrown at this point.

"It's always been that way" is similar to "it was invented here" in that regard. Besides, the imperial units had local versions and some still do. There are AFAIK no US inches and yards, but US gallons and US pints.

You might be surprised at how many Americans think that Jesus spoke English.

Source: am American.

Trusting us Americans to know history? Not a chance.