“Pocho” is a term for a Mexican who lives in the United States. “Pochismo” is an English word given a Spanish form or pronunciation.
 
“Pocho” is generally regarded as derogatory and should rarely be used.
   
   
(Oxford English Dictionary)
pocho, n. (and adj.)
Chiefly U.S. (depreciative).
[< Mexican Spanish pocho (a1928 in this sense) < Spanish pocho discoloured, faded, pale (1817), of imitative origin. Cf. POCHISMO n.] 
A Mexican who has adopted American cultural values; a U.S. citizen or resident of Mexican origin. Also attrib. or as adj.
[1931 Los Angeles Times 25 Oct. (Sunday Mag. section) 5/2 The Mexican born in California smarts under the nickname ‘pocho’, with the feminine ‘pocha’.] 1944 Newsweek 14 Aug. 76/3 A pocho in good standing will drag his fititoes (feet) up the estrita (street). 1944 Newsweek 14 Aug. 76/3 Slapstick actors like Tin Tan..who gets comic effects with pocho patter.
     
pochismo, n.
[< Mexican Spanish pochismo (1936 in the source discussed in quot. 1937 at sense 2) <

pocho POCHO n. + -ismo -ISM suffix.] 
1. An English word which has been given a Spanish form or pronunciation; a form of slang used by speakers of Mexican Spanish and others along the border with the United States, consisting of such words. Cf SPANGLISH n.
1944 N.Y. Herald Tribune 5 Aug. 10/3 The Mexican Academy has appointed a committee to eradicate ‘pochismos’ that is English words and phrases used in speaking Spanish. 1944 Newsweek 14 Aug. 76/3 Café society which uses pochismo to smart up its chitchat.
2. depreciative. Excessive admiration in an Hispanic (originally a Mexican) American for the culture of the United States.
[1937 Hispanic Amer. Hist. Rev. 17 82 This philosophy, whose advocates are North Mexicans, he [sc. José Vasconcelos] calls ‘pochismo’, which strives for the overthrow of Hispanic culture and civilization where it flourishes most in Mexico City.]
       
Time magazine
Authentic Pachuco
Monday, Jul. 10, 1944
Every night last week flashy, rowdy crowds formed around a dirty Mexico City music hall called the Folies Bergere. Even at ii o’clock, when the second show began, they stormed the doors and raced up to the gallery. They were there to see Mexico City’s popular clown—zoot-suited, 27-year-old Tin Tan (real name: German Valdes), billed as “The Only Authentic Pachuco.”*
 
Tin Tan can plummet his voice from coloratura soprano to Chaliapin bass. But-it is not his voice that enthralls his fans, it is his lingo. For Tin Tan is a master of pocho, and pocho, a bilingual bastardy of anglicized Mexican,† is as funny to Mexican ears as the English of a stage Englishman is to Americans. Pocho, which literally means something that has lost its color, has come to stand for the thousands of Mexicans near or across the border who have ruined their Spanish without ever quite learning English. To aficionados Tin Tan is high satire.
(...)
* Mexican for zoot-suiter.
† Watermelon, doughnuts, shampoo (in Spanish, sandla, rosquitas, lavar la cabeza) become guaramelon, donas, champu, in pocho. Outside the Folies Bergbre hawkers sell a pocho glossary.
   
26 July 1944, Lowell (MA) Sun, pg. 11, col. 1:
Exterminate
“Pochismos”
 
It’s Battle Cry of the
Mexican Language Academy
 
MEXICO CITY, July 26. (AP)—The Mexican Language Academy has appointed a committee to seek to exterminate “pochismos”—English words or words of U. S. origin used in speaking Spanish.
 
The committee will compile a list of “pure” words to substitute for current pochismos and send the list to teachers, radio announcers, newspaper editors and actors.
 
The word pochismos comes from pocho, a Mexican living in the United States.
 
Pochismos include bittle, meaning bookie; marqucia, meaning market; farma, for farm; bordo, for boarding house; guachear, meaning “to watch” and truca, for truck.
 
15 September 1951, Saturday Review, pg. 61, col. 1:
Mexican-American Slang
(...) This slang is called pochismo which itself is derived from the word pocho, the colloquial Mexican term for a Mexican-American. It is, in fact, spoken not only by thousands of Mexican immigrants in the United States, but as well by Mexicans living below the Rio Grande. All along the border, on the American and Mexican side, and as deep into the USA as Saint Paul and Detroit, the words the pochos have coined are of current use. Some words belong to the everday speech of Monterrey and Tiajuana, while others, carried by “wetbacks,” have reached Mexico City. Undoubtedly, Ciudad Juarez may well be called the capital of “Pochilandia,” unless, of course, San Antonio (Tex.) claims this linguistic privilege.
 
The word pocho became of current use about fifteen years ago with the publication of Jose Vasconcelos’s autobiography “Ulyses Criollo.” To describe an individual as pocho is a mixture of affection and insult. The word was needed and stayed. Better than any other it describes the hybrid mixture of U.S. attitudes in the Mexican mind.
 
Not a single pochismo has added to the beauty of our Spanish language; on the contrary the new words are ugly, hard to listen to, and difficult to read.
 
6 November 1953, Yuma (AZ) Daily Sun, pg. 16:
Considering that “pochismo” as that degeneration of the Spanish language is called down south of the border, it is dangering the purity of our traditions. The federal government through the Interior Department made recommendations to all governors to battle such thing.
 
Attending to these recommendations, Governor Soto had asked to all business owners, that have their signs in English or “pocho,”  swept it away in order to replace those names with its equivalent in correct Spanish. That means that signs like “Telle’s Cafe,” “Curios Shop,” and “International Club” that can be seen at San Luis will be changed to “Cafe Tellez,” “Casa de Curiosidades” and “Club Internacional.”
 
Those that don’t like “pochismo” welcomed the measure and commented that it was necessary since a long time ago. 

Mexico Revisited
by Erna Fergusson
New York: Knopf
1955
Pg. 20:
The border speech is pochismo, a hybrid of Spanish and English, named from pocho, a slang word for the Mexican-American. Jose (Pg. 21—ed.) Vasconcelos first used these words in print in his autobiography, Ulises Criollo.  Scholars hate pochismo; they say it has added no beauty to the language.
 
Google Books
Society and Health in the Lower Rio Grande Valley
by William Madsen
Hogg Foundation for Mental Health
University of Texas
1961
Pg. 9:
In South Texas, the Spanish-speaking people from New Mexico are called “manitos” and those from California are known as “pochos.” In Mexico the term “pocho” ...