but后面的介词短语和of strong words from the region 并列。

but 是并列连词，后面不完整是因为承前省略成分的缘故。补全为：

I think the reaction to the decision is going to be one of strong words from the region, but it is going to be one without much action taken.

it 指代前文的the reaction to the decision。

如果一字不漏的全部补齐，就啰嗦极了：

I think the reaction to the decision is going to be one of strong words from the region,  but the reaction to the decision is going to be one without much action taken.

看得出，one 之后的蓝色部分，才是真正的并列成分。