Check your state's laws on the matter.
Sexual assaults and/or sexual batteries are usually defined and differentiated with some rather specific and graphic language.
I'll admit I'm not educated on these matters. I had the impression that sexual assault covered everything these days.
Here's what I find at a mass.gov site, which seems to support your comment.
Sexual assault and rape are crimes of violence and control, using sex acts as a weapon. Rape and sexual assault are not sexually motivated acts; rather, they stem from aggression, rage, sexism, and the determination to exercise power over someone else. Rape is also a legal term that is defined in Massachusetts by three elements: penetration of any orifice by any object; force or threat of force; against the will of the victim. Sexual assault is often more broadly defined as any sexual activity that is forced or coerced or unwanted.
I'm a little annoyed to see the highlighted bit on a page purporting to define sexual assault and rape. Doesn't seem to me that motive is part of the definition, nor that it's obvious that sexual motivation is irrelevant (or how one would establish that claim).
But this is a minor aside. The main point is that, at least in my state, you're absolutely right that there is still a fairly clear line between rape and assault. (There does seem to be the problem that a woman forcing a man to penetrate her isn't committing rape and we can argue whether that's strictly speaking fair or not, but I think that in practice, it is inconsequential. I'm not going MRA here, for goodness' sake!)
