Well the alternative in the US is to go somewhere with a big merit scholarship and save your money. For example my D chose Utah (which offers 30 full rides per year) over UCB and UCLA. Although admission is straightforward (and they have auto merit up to full tuition), the top scholarships are judged more holistically. The same would apply to top merit scholarships at other big universities.
Utah have a strong math department (one of my classmates was actually a professor there after doing his PhD at Caltech) and have sent the top math or science student to Cambridge with a Churchill scholarship every year for the last four years (eg https://unews.utah.edu/university-of-utah-student-awarded-prestigious-churchill-scholarship-3/). They offer lots of support and opportunities for the top students, far more than her twin brother gets at UCLA. She’s having a great experience (not doing math) and saving $100K over our instate rates. Many CC posters have had similarly positive outcomes with merit elsewhere. Going to Cambridge for Part 3 maths (whether with a scholarship or with the money you saved in undergrad) and doing well there is an entry point into any top PhD program.
So I would tend to keep the fourth year of social studies and Spanish in the schedule, especially as you’ll want to make UIUC admission more certain also.