(US) Company just got acquired, do I still owe back my signing bonus?

Location: Colorado, USA

I started a new job last July. I negotiated for 4 weeks of vacation and a 30K signing bonus with the condition that, if I left before 2 years, I would owe back my signing bonus. We were recently acquired, and as a part of that acquisition, the new company paid out our accrued vacation and switched us to a new "unlimited" paid time off model. Since I had negotiated for 4 weeks of vacation, I considered this a breach of contract, and asked HR if I was still obligated to pay back the 30K if I left before two years, and they said that I was. Is this enforceable? This is not the contract I agreed to on hiring, and by removing my 4 weeks of vacation, I believe my initial contract is in default.

Thank you for your help.

Author: SpasticBannana