Bicycling magazine's website has a forum discussion about the top ten
American cyclists. I didn't find it especially interesting, except for this
post, which I've cut and pasted (without permission):

Walter Bardgett was considered the outstanding authority on bicycle racing
in America until his death in 1953. Bardgett raced all over the world from
1898 until about 1918 and was rated highly. Retiring from competition,
Bardgett became editor of the "American Bicyclist", the only regularly
published cycling magazine in this country, and also reported regularly for
various European publications. Always asked repeatedly for his Top Ten, he
always named fifteen, it being his contention that he could not limit the
list to ten. With the exception of Reggie McNamara, Bardgett did not
consider any rider after 1930 up to the same caliber of thos on his list
because the professional sport had waned in this country ever since the fire
that destroyed the New York Velodrome in 1929. (Which btw some riders felt
was set by a certain rider that was pissed off at John Chapman). Bardgett's
selections follow: (first three are in order of preference; the others were
rated of equal ability):

Frank L. Kramer, East Orange, NJ

E.C. (Cannon) Bald, Buffalo, NY (later of Pittsburgh, PA)

Iver Lawson, Salt Lake City, UT

Tom Butler, Cambridge, MA

Tom Cooper, Detroit, MI

Owen S. Kimble, Louisville, KY

Earl Kiser, Dayton, OH

Willie Fenn Sr., Waterbury, CT

Floyd McFarland, San Jose, CA

Nat Butler, Cambridge, MA

Bobby Walthour Sr., Atlanta, GA

Major Taylor, Worcester, MA

Alfred Goullet, Newark, NJ

Reggie McNamara, Newark, NJ

Jackie Clarke, Newark, NJ

It should be noted that the last three on the list came from Australia and
became United States citizens.

The above are all track riders, some world champions, all raced here in the
US and in Europe against the best riders of their era.

Reggie McNamara would be one racer on the list I would say could have raced
in the tour and one day classics and won multiple times. He was tougher than
nails and looked it too.

Goulett was most famous for six day racing. He and his partner Alf Grenda
rode 2,759 miles in six days.

Now the "go as you please" One Man six day race record is held by Charlie
Miller. He rode 2,093.4 miles in 142 hours in 1898. Team format (modern day
Madison) started in 1899.