No, it is wrong. Some Americans in the northern states did oppose slavery. However, there were many Americans in the south who fought to save the confederacy which supported the legalisation of slavery. And even today, Americans have hundreds of monuments dedicated to the Confederacy and to those who fought to preserve the Confederacy which supported the enslavement of innocent people.
For example, in Arkansas, we see (from wikipedia):
Arkadelphia Confederate Monument, Arkadelphia, Arkansas, listed on the National Register of Historic Places in Clark County, Arkansas
Batesville Confederate Monument, Batesville, Arkansas, listed on the National Register of Historic Places in Independence County, Arkansas
…
Jackson Guards Memorial, Newport, Arkansas, built in 1914. Monument consists of a statue of a single Confederate soldier and a roster of the men who served in the Jackson Guards and the slaves who supported them. The only Confederate monument in Arkansas built entirely with funds raised by private subscription.[14]
Pine Bluff Confederate Monument, Pine Bluff, Arkansas, listed on the National Register of Historic Places in Jefferson County, Arkansas
Searcy Confederate Monument, Searcy, Arkansas. Erected in 1917 on the grounds of the White County courhouse. Listed on the National Register of Historic Places in White County, Arkansas. Consists of a statue of a Confederate soldier.[14]
Star City Confederate Memorial, Star City, Arkansas. Erected in 1926 in the courthouse grounds, moved in 1943 and moved again to original position on town square in the 1990s. Listed on the National Register of Historic Places in Lincoln County, Arkansas. Consists of a statue of a Confederate soldier.[14]
Van Buren Confederate Monument, Van Buren, Arkansas, listed on the National Register of Historic Places in Crawford County, Arkansas
Washington Confederate Monument, Washington, Arkansas, listed on the National Register of Historic Places in Hempstead County, Arkansas
In Kentucky we see:
Confederate Monument in Augusta, Augusta, Kentucky
Confederate Monument of Bardstown, Bardstown, Kentucky
Confederate Monument of Bowling Green, Bowling Green, Kentucky
Confederate Monument of Cadiz, Cadiz, Kentucky
Confederate Monument at Crab Orchard, Crab Orchard, Kentucky
Confederate Monument in Cynthiana, Cynthiana, Kentucky
Confederate Monument in Danville, Danville, Kentucky
Confederate Soldiers Martyrs Monument, Eminence, Kentucky
Confederate Monument in Frankfort, Frankfort, Kentucky
Confederate Monument in Georgetown, Georgetown, Kentucky
Confederate Monument in Glasgow, Glascow, Kentucky
Confederate Monument in Harrodsburg, Harrodsburg, Kentucky
Confederate Memorial Fountain, Hopkinsville, Kentucky
Latham Confederate Monument, Hopkinsville, Kentucky
Unknown Confederate Soldier Monument, Horse Cave, Kentucky
Confederate Martyrs Monument, Jeffersontown, Kentucky
Confederate Monument in Lawrenceburg, Lawrenceburg, Kentucky
John Hunt Morgan Memorial, Lexington, Kentucky
Ladies’ Confederate Memorial, Lexington, Kentucky
Confederate Monument in Louisville, Louisville, Kentucky
Confederate Memorial in Mayfield, Mayfield, Kentucky
Confederate Memorial Gates in Mayfield, Mayfield, Kentucky
Martyrs Monument, Midway, Kentucky
Confederate Monument of Morganfield, Morganfield, Kentucky
Confederate Monument of Mt. Sterling, Mt. Sterling, Kentucky
Confederate Monument in Murray, Murray, Kentucky
Confederate Monument in Owensboro, Owensboro, Kentucky
Confederate Monument in Owingsville, Owingsville, Kentucky
Confederate Monument in Paducah, Paducah, Kentucky
Bourbon County Confederate Monument, Paris, Kentucky
Confederate Monument in Perryville, Perryville, Kentucky
Confederate Monument in Russellville, Russellville, Kentucky
Confederate Mass Grave Monument, Somerset, Kentucky
Confederate Monument in Versailles, Versailles, Kentucky
That’s only two states. How many other states have monuments dedicated to the Confederacy?
See:
en.wikipedia.org/wiki/Confederate_monuments