The mexicans were originally a tribe terrorised by the Aztec blood cult, apon the arrival of the Spanish, they instantly realised they were inferior and helped the Spanish eradicate the Aztecs in return for the honour of adopting their culture. Those who still thought blood sacrifices are neccesary to make the sun go round illegally migrated north.
Many native americans realised their culture was inferior when the Puritans arrived and peacefully helped build early america. The native americans were split between the intelligent who wanted to go from neolithic farmer to rennaissance settlers and tradesmen and the stupid native americans who fled west and degraded into an inferior tribal culture. The intelligent native americans intermarried with the Puritans and wisely abandonned their inferior culture, so their descendants lost many of their mongolid traits to the larger populations of whites living there. The stupid native americans were naturally the most hostile, a far cry form the native who helped settlers during thanksgiving and unfortunately they scalped those who attempted to make contact with them, so eventually the settlers gave up and just shot them on site.
It wasn't a case of relations souring between whites and natives, but of the presence of civilisation dividing the natives between those who wanted not to see their children starve each winter and the crazy paranoid native who blame the white man for everything. A similiar process which occurs with non-whites in the presence of white civilisation today, in particular the African American community. Conservative African Americans are some of the finest human beings on the planet, disciplinned intelligent charismatic people who make a real contribution to western culture. A far cry from the stupid liberal African Americans who prefer to degrade to barbaric tribal/gang culture, steal things, sell and take poison and force women into prostitution instead of participating in civilisation and of course blaming all their problems on the white man.