The source for the American dead is the American Battle Monuments Commission. As their site states, they only list those actually buried or commemorated at the monuments they maintain,

Of the 136,516 Americans that lost their lives during World War I, there were 4,452 Missing in Action. Of the remainder, the next of kin of 30,921 elected to have their loved ones buried at our cemeteries. Below is a listing by cemetery showing the number buried and the number that were declared Missing in Action in the vicinity of the cemetery. The listing of the World War I database, now on the web contains the 33,714 names of those buried at our cemeteries, those Missing in Action and those buried or lost at sea. It does not contain the names of the 101,143 Americans returned to the United States for burial.

American Blackburns killed in World War One - source

British and Commonwealth Blackburns killed in World War One - source

There are nearly 500 Blackburns listed amongst the 1.7 million names in the Commonwealth Graves Commission Debt of Honour database, Link here. This remarkable resource gives details of the circumstances of death and the locations of the graves for each one.