We can have a look at what the Bibles preceding the KJV said:

Isaiah 40 Wycliffe Bible (1394)

22. Which sittith on the cumpas of erthe, and the dwelleris therof ben as locustis; which stretchith forth heuenes as nouyt, and spredith abrood tho as a tabernacle to dwelle.

Isaiah 40 Tyndale Bible (1531)

22. [It is] he that sitteth upon the circle of the earth, and the inhabitants thereof [are] as grasshoppers; that stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in:

Isaiah 40 Coverdale Bible (1535)

22. That he sytteth vpon the Circle of the worlde, and that all the inhabitours of the worlde are in coparison of him, but as greshoppers: That he spredeth out the heaues as a coueringe, that he stretcheth them out, as. a tent to dwell in:

Isaiah 40 Matthew Bible (1537)

22. That he sytteth vpon the circle of the worlde, and that al the inhabytours of the worlde are in comparison of him, but as greshoppers: That he spredeth out the heauens as a coueryng, that he stretcheth them out, as a tent to dwell in:

Isaiah 40 Geneva Bible (1560)

22. He sitteth vpon the circle of the earth, and the inhabitants thereof are as grashoppers, hee stretcheth out ye heauens, as a curtaine, and spreadeth them out, as a tent to dwell in.

Isaiah 40 Bishops' Bible (1568)

It is he that sitteth vpon the circle of the world, whose inhabiters are [in comparison of him] but as grashoppers: he spreadeth out the heauens as a couering, he stretcheth them out as a tent to dwell in.

They all been translating this as circle. The correct word to use, is circle. Only the Jesuit trained Priest are claiming otherwise.