Sher, 
You are mistaken ‘Hispanics are by definition a mixed race’. According to the US Census Bureau, Hispanics can be of any race; white, black, native Indian and in between. The vast majority identify as white. It is not up to you to decide how they identify. 

When Florida was ruled by Spain, never by Mexicans, its population was mostly Native Indians. It was annexed in steps; it became completely American by 1821; pop in 1830 was 35,000.  

The American Southwest was ceded by Mexico in the Treaty of Guadalupe Hidalgo in 1848; many of its Spanish/Mexican settlers wanted the territory to be annexed to a country with less turbulence than Mexico. 100,000 Mexicans lived in the areas ceded, like California, New Mexico and Texas. Residents had the choice of relocating to Mexico or receiving American citizenship with full civil rights. The two main Republican contenders against Trump were two Hispanic-Americans, Senator Marco Rubio, Florida and Senator Ted Cruz, Texas.