Is a 650 on the US History SAT bad?
Depends on what schools you are applying to. For most it is a good score.
Most schools don’t require or even mention subject tests; in that case you should only send the score if it truly reflects ability over and above what your grades or AP/IB curricula or exams already demonstrate. Don’t send in the score just because you think schools like subject tests. Many don’t care, and a test that demonstrates poor aptitude relative to grades or AP/IB might actually harm your chance for admission. If you had a 700-750 instead of a 650 this obviously wouldn’t be an issue (but then you wouldn’t have needed to post . . . ). Think carefully before sending your score and make sure it is consistent with the goals you have for your application. @TomSrOfBoston is correct: it depends on what schools you are applying to. I’d also add: it depends on what else is in your application.