What steps can US undergraduates take to reduce the frequency and severity of assignment of unearned grades, as from grade inflation and cheating?
Grade inflation is not happening because of academic misconduct.  That has zero to do with it.  Most of us are surprisingly good at spotting plagiarism and we give out a depressing number of zeros for that and other forms of misconduct.  Trust me, very few of those students are contributing to inflation.

Grade inflation is a long-term slow trend.  Most instructors try to grade "about like" their colleagues in the department.  But few of us want to seem unfair, so we err on the side of being a bit generous. Over time, you get inflation.

But go for it.  If you came to me, pleading for a tougher curve and a lower grade, you'd definitely be my first.  I would certainly remember you.