U.S. residents simply haven’t been indoctrinated into the SI units. Miles, pounds, ounces, yards, etc. are labeled everywhere so people get a feel for them from a very young age. They just don’t know the SI unit sizes- or so it would seem.

What may be necessary to instill some confidence in younger folks is to point out the units they already have a feel for but don’t know they do.

Grams- all U.S. currency notes have a mass of one gram each.

Liters- this one most people know. A liter is one quart plus an extra gulp. They don’t know one liter of water is one kilo. Therefore, those 500 ml bottles of water everyone totes around these days are a half kilo plus a few grams for the bottle, or just over one and one tenth of a pound.

A half kilo of ground beef would be the same as a pound plus a bite or two more.

Speedometers are informative- 50 mph is just about 80 kph which means one km is about 5/8 of a mile.

61 F = 16 C (approximately)

I found teaching the units this way made the students (9th graders) more comfortable when using the SI units.