This sentence is... strange.
The general consensus is that most people consider Southerners to be friendly
It means: the consensus is NOT about "Southerners are friendly", but about "most people consider this and that". Or did I understand it incorrectly?
"General consensus" can be translated as "普遍共识", but this is too official, often used in government documents or the news. Also, this is a noun, not a verb.
Orally, people say 人们普通(一般)认为 this and that.
So, it's " 人们普通认同 '大多数人都认为南方人很友善' ". :-D
Or it's "人们普通认同南方人很友善(的看法)".
The second sentence means different. It's more objective and seems to be stating the fact. So it's "南方人的普遍特征是他们很友善".