Above is the a link to the 1856 Griffiths Valuation head of household for Claregalway civil parish. There is a Thomas Collins in Carnmore West townland. Possibly the brother to James.
I also checked the 1901 and 1911 census records for Carnmore West and there was a Thomas Collins and his wife and son in both censuses. See above.
I did not find any Collins records in the Tithe listings.
Claregalway parish is near the Co. Clare border rather than the Mayo side so I assume James met Catherine in America.