If USC is your spring admit school, why do you think you will find out that you are bumped in May? Did someone tell you that? In the past, it has been much later, some people that got bumped didn’t know well into June and even later July. Agree with @Lindagaf, what does the SIR say? The deposit date is irrelevant to the decision in terms of what is right and allowed, you are committing May 1st.
Per USC Spring Admit page:
You can attend a CC or gap it or one of the abroad universities…
Four-Year Options
Do not enroll in a four-year college under the false pretense of finishing your degree there.
Last year was a whacky year (and of course, this year is it’s own kind of whacky) and people were bumped to fall, in past years, it was common for there to be no bumps to fall.
I get missing fall stinks, but if you would quickly pick another school if you are only getting into USC in the spring, I think you have to ask yourself how important attending USC really is to you?