Why did the South prove to be more difficult to conquer than the British expected?

There were multiple reasons, and most of them were really just because the British failed to take control. (More in the explanation.)

Explanation:

The British assumed that they had loyalty among their numbers, traitors were active. The British failure to deploy sufficient forces to take control of the South.

you didn't give any answers to choose from so i can't with this but, i do know something that the mexican government would be worried about and that is the wall that donald trump is currently trying to get up.

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain