Need help with visa extension, stamping, and traveling out of US

I am in an unexpected situation for myself and want help confirming next steps.

• My H1-B was recently extended from Feb, 2026 to Dec, 2027.
• My passport still has the old stamped visa ending Feb. 2026.
• I want to travel to South America since I am burned out in Dec.

Can I travel with my visa ending in Feb. 2026 stamped in passport? Or will I not be allowed back to US since the newest visa is not stamped?

Any help is appreciated.