here are a few:
"All government, in its essence, is a conspiracy against the superior man: its one permanent object is to oppress him and cripple him. If it be aristocratic in organization, then it seeks to protect the man who is superior only in law against the man who is superior in fact; if it be democratic, then it seeks to protect the man who is inferior in every way against both. One of its primary functions is to regiment men by force, to make them as much alike as possible and as dependent upon one another as possible, to search out and combat originality among them. All it can see in an original idea is potential change, and hence an invasion of its prerogatives. The most dangerous man to any government is the man who is able to think things out for himself, without regard to the prevailing superstitions and taboos. Almost inevitably he comes to the conclusion that the government he lives under is dishonest, insane and intolerable, and so, if he is romantic, he tries to change it. And even if he is not romantic personally he is very apt to spread discontent among those who are.
-H.L. Mencken 1919"
There is no room in this country for hyphenated Americanism... a hyphenated American is not an American at all. This is just as true of the man who puts "native" before the hyphen as of the man who puts German or Irish or English or French before the hyphen. Americanism is a matter of the spirit and of the soul. Our allegiance must be purely to the United States. We must unsparingly condemn any man who holds any other allegiance. But if he is heartily and singly loyal to this Republic, then no matter where he was born, he is just as good an American as any one else.
The one absolutely certain way of bringing this nation to ruin, of preventing all possibility of its continuing to be a nation at all, would be to permit it to become a tangle of squabbling nationalities, an intricate knot of German-Americans, Irish-Americans, English-Americans, French-Americans, Scandinavian-Americans or Italian-Americans, each preserving its separate nationality, each at heart feeling more sympathy with Europeans of that nationality, than with the other citizens of the American Republic. The men who do not become Americans and nothing else are hyphenated Americans; and there ought to be no room for them in this country. The man who calls himself an American citizen and who yet shows by his actions that he is primarily the citizen of a foreign land, plays a thoroughly mischievous part in the life of our body politic. He has no place here; and the sooner he returns to the land to which he feels his real heart-allegiance, the better it will be for every good American. There is no such thing as a hyphenated American who is a good American. The only man who is a good American is the man who is an American and nothing else.
For an American citizen to vote as a German-American, an Irish-American, or an English-American, is to be a traitor to American institutions; and those hyphenated Americans who terrorize American politicians by threats of the foreign vote are engaged in treason to the American Republic
Theodore Roosevelt, 1915 - speech to the Knights of Columbus.
and a personal favorite:
It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat.
― Theodore Roosevelt