My country'tis of thee这句话怎么不通顺的感觉?

问题描述:

My country'tis of thee这句话怎么不通顺的感觉?
I have a dream里面的句子
My country'tis of thee,sweet land of liberty,of thee I sing.
我查了字典'tis是it is的缩写,这里也是这个意思吗?那不就是My country it is of you的意思了?My country it is貌似有点问题吧
还有就是of thee I sing怎么译?

tis =that is