I felt it so difficult to live in an english-speaking country that i determined to learn english.
这里是部分倒装,部分倒装提前的是be动词或助动词,也就是说没有be动词的情况下,找到对应的助动词提前,felt是一般过去时,所以提前did.这里的部分倒装有点像是陈述句变一般疑问句的步骤.
it做的是形式宾语,指代to live in an english-speaking country that i determined to learn english