Answer:
So, Mexican Cession was own by mexico and Disputed Texas Territory was being in a little war. *AMERICANS* and the *MEXICANS* were fighting each other for the ownership of Texas
Explanation:
Americans won. Because they had more efficient weapons and were (CHEATING IS WHAT MY TEACHER SAID IN 8TH GRADE). Mexican Cession I don't really remember. And Oregon was either not own or own by Canada.
So I hope this helps.