Germanic integration in America (as well as other large Western nations like Canada and Australia) has been relatively smooth overall, for the gamut of reasons many here have suggested. German immigrants were valued for their skills, education, work ethic, fortitude, etc. as Fred noted [Arbeit macht das leben s�ss!]. As all know, many of the developing Western countries of the modern era were founded (invaded, your choice) by the English, who were and are racial cousins of the Deutsch on the continent, with obvious and substantive cultural/religious overlappings. But perhaps even more telling is the fact that the largest ethnic group, at least in the United States, is constituted of German Americans [58 million at last count], whose numbers far exceed those of English or Irish backgrounds, and by substantial margins (the Irish and English being the next largest groups, perhaps soon to be eclipsed by the Mexicans - our growing version of the Turks - but that's another story).
A degree of anti-German sentiment did spread as German immigration numbers grew in untold leaps and bounds. The Germans were accused by many 18th century Anglos of laziness, illiteracy, clannishness, a reluctance to assimilate, excessive fertility, and Catholicism. They were even blamed for the severe Pennsylvania winters! {{{Yikes}}}
However it was the anti-German propaganda of World War I that actually bordered on the criminal. It was arguably more stringent than that of WWII. In the 19th century, it was not unusual to see references to Germans (euphemistically or colloquially) as 'Teutons'. It was a neutral word that had no negative connotations per s�. During WWI that changed. The Germans, who the Wilson administration were lining in the crosshairs for a showdown, were almost uniformly referred to as 'Huns' in the press and wires across the country, and in a most derisive way (with the obvious insinuations to the bloodthirsty Huns of Attila's day).
Such attitudes had a chilling effect on language use. During this time most of the states dropped German from their school curricula. [In fairness though, the anti-German school laws were later declared unconstitutional by the U.S. Supreme Court, circa 1923]. However as many as 18,000 people were charged in the Midwest during and immediately following World War I with violating the English-only statutes. [It was no myth Mona!]
Notwithstanding the persistent legend that German missed becoming our official language by a single vote (through a century of claims by the likes of Ripley's Believe-It-or-Not, Parade magazine, certain authors, etc.), American English has never been in any real jeopardy. At no time in our early (colonial) history was the percentage of Germans in the United States ever higher than about ten percent, and hardly in position to upset the cart (ergo, status quo). The reality is, Americans have never had a legally established official language! That said, no other language or tongue has ever had equal status with English, from colonial times to the present day.
It goes without saying that Germans have played an important, even crucial, role in the history and development of America (and most other Western countries). Their stamp is all around us in ways too numerous to count, even in the Germanic (Anglish) tongue we speak. But assimilative forces were - and are - hard to resist. Most of Anglo-German blending and social change, here and elsewhere, came from ethnic assimilation, industrialization, road-building, electrification, mass media, and the passing of isolated rural life, and in the end far less from legislation, persecution or intimidation.
Jb