a poli sci
Maybe. Most don't take it, some would spit on it as not a real science.
or government class
Definitely not taught that way.
knows the difference between liberals and leftists
Nope.
When the right talks about owning the libs, they're not talking about owning themselves, they're talking about leftists including center-leftists.
the US is widely uneducated
That's not why. Mainstream TV news media in the US refers to left & liberal interchangeably. These aren't uneducated people. The meanings just differ by continent.
Until you brainwash & reeducate the bulk of North America, that's the meaning of those words there, and to them your distinction is pretty senseless. Facts. Deal with it.
Moreover, the pedagogic meanings of left & liberal aren't even mutually exclusive. Leftism is politics that pursue social equality & egalitarianism. Liberalism is politics that pursue personal freedom. These clearly can intersect as politics that pursue all 3, eg, social liberalism, a center-leftism that
stress[es] civil and human rights and favour[s] a social market economy.