If you can’t parse the difference between “collision ahead” and “use yah blinkah”, then you shouldn’t be driving at all.
“Immigrants” are not uniquely unable to parse these things.
About 1.5 billion people drive on left (India, UK, Australia, Japan, Singapore, Malaysia....). Road sign "to the left" has VERY important meaning for big part of globe. Some people travel a lot and change left/right driving a few times every month..
But perhaps Beyonce songs and American pop culture, should be part of driving exams globally! So everyone can parse your "funny" jokes.
The people writing these messages are part of the DOT. Not surprisingly they already think of this stuff. They’re not stupid.