The problem is that there were so many Corkills that you need additional information to be sure you have the correct Thomas.

Maughold par regs have:
Thomas son of Thomas Corkhill & Margaret Fargher bapt. 29 Nov 1812.

Thomas son of Patrick Corkill & Catharine Creech bapt. 15 May 1814.

There are several others in the IGI bapt Lonan, German, Braddan, Rushen.

Without additional identifying info. in the USA [e.g. birth date on MI], you could try ordering a lot of LDS wills films using the names and possible dates of death of all these parents who appear in Brian Lawson's will index. Wills often mentioned children in the USA or "beyond seas", or in a specific place overseas.

Sue