1911 Ireland Census: www.census.nationalarchives.ie
I'm assuming he was born in 1899? if not this won't be right.
There are lots of Dowd/O'Dowds name John in either Cavan or Monaghan but in 1911 he would be around 13.
#7 Drumhurt, Tullyvin East(Rural Cavan)
Mary Dowd age 45 Bellringer, born Cavan, Widow
John 13 born USA, at school
Annie 11 born USA, at school
Catherine 9 born USA, at school
None the right age in Monaghan.
His sisters would have married and changed names, so you will need to wait for a family member to spot this.
You are posted on the Armagh message board so if you haven't done it already you should post again on CAVAN Co.message board.
There are too about 30 Dowd/O'Dowd's in the current telephone book to many to make any guesses as to perhaps cousins?
Drumhurt was a Townland in the Parish of Kildrumsherdan and in the Union of Cooterhill. Which means within 12 mi. of
Cooterhill. The phone book has 2 listings, one Dowd & one
O'Dowd in the Cooterhill area. Addresses given are sufficient for mail delivery.
Not being any relation to the Dowd family that's about all I can do to help.