the average American doesn’t know a meter from a hole in their ass

Do they actually know yards? A metre is pretty close to one yard. If you know yard, you know the metre.

But they do know litres, because the big soft drink bottles are sold in litres. They know grams if they do drugs or bake. They know prefixes like Mega, Giga and Tera if they are into computers, and they know about "kilo" if they pay an electrical bill. If they're into military stuff, they know about "clicks", which are actually... kilometers.

I think it's slowly creeping in.

Normalize it. Use meters and kilograms on your own even before legislation. Convince others to use it. Push back the storm. If a handful of people in your town use it then it goes from something that nobody uses to a thing that a few people (and the rest of the world) use. Be the change you want to see.

"The story of the metric system starts, somewhat unexpectedly, in 17th Century England, with the proposal by the natural philosopher John Wilkins for a consistently decimal system of units. The Europe of his time was divided by the use of innumerable different systems of measure, with each country using its own traditional units (and in many cases, a lack of even national standardisation meant that different regions within countries would use their own measures). To remedy this, Wilkins conceived of a single, rational standard, based on the best science of his time, which all nations could equally share. His idea for a “universal Measure” was not adopted in his era, although that very phrase would ultimately (via Greek translation) give us the name of the metre."!