Better race relations:
How about a more equitable and effective Reconstruction, for starters, where the federal govt effectively and competently defends the rights of blacks and empowers them politically and economically in the ex-Confederacy, while undermining the power of the Klan and other white supremacist terrorists and destroying any image of a set black vs white racial conflict so that the majority of Southern whites are able to see ex-slaves as partners and friends with whom to build a peaceful future together, instead of OTL many whites being taken in by KKK-manifested fears of black rampant criminality and desire to revenge themselves on all whites. There'll also need to be a greater acceptance of blacks in the North and other parts of the country, too, so let's facilitate some sorta effective federal govt civil rights intervention in northern states to outlaw and undermine racial discrimination which OTL had been enacted by some northern states and major cities. Such federal laws would've also required the undermining of popular media stereotypes of blacks as lazy, shiftless, criminally-inclined brutes with uncontrollable sexual appetites. Another important hypothetical which has been previously discussed is in integrating the entire US armed forces so that a bond of brotherhood could be formed by men of all race serving, fighting and dying alongside each other. Possibly another war against a foreign power as soon as possible after 1866, such as over the 1873 SS VIRGINIUS affair against Spain as speculated in the previous board, would've galvanised collective American opinion and endeavour among all citizens towards a common end, thereby forging a greater degree of mutual respect among ppl of different races. These listed changes IMHO would've had a tremendous positive impact on the hist of American race relations post-CW.
In addition, there'd have to be other changes re other minority groups, esp Indians, Hispanics and Asians. How about the development of a more inclusive frontier ethos in the popular media, combined with the US govt's more equitable treatment of native American tribes (ie properly providing surrendered Indians on reservations with sufficient rations instead of OTL Indian agents virtually starving Plains tribes with bad food and compelling them to go back on the warpath) and passage of effective anti-discrimination laws to outlaw discriminatory behaviour against ppl of any and all races ?