Showing our age perhaps but you can’t have a list of American male singers and not have Elvis Presley on it.
He suffers from the trash he sang from 1960 on but for pure ability, range and the fact he could sing the phone book and it could sound good he has to be on the list.
The rest is subjective.
How about a vote for Enrico Caruso and Robert Merrill?
Post ‘60 ‘Kentucky Rain’ and “In The Ghetto’ were okay numbers by the King, not in the trash category imho.