“Had President Kennedy not pledged the nation to bear any burden, meet any hardship, support any friend, and oppose any foe to assure the survival and the success of liberty?”

Radio adress (January 13, 1953), as quoted in Philip Short (2004) Pol Pot: The History of a Nightmare, page 83.

Conditions of Progress in Democratic Government (1909).
Context: No greater mistake can be made than to think that our institutions are fixed or may not be changed for the worse. … Increasing prosperity tends to breed indifference and to corrupt moral soundness. Glaring inequalities in condition create discontent and strain the democratic relation. The vicious are the willing, and the ignorant are unconscious instruments of political artifice. Selfishness and demagoguery take advantage of liberty. The selfish hand constantly seeks to control government, and every increase of governmental power, even to meet just needs, furnishes opportunity for abuse and stimulates the effort to bend it to improper uses... The peril of this Nation is not in any foreign foe! We, the people, are its power, its peril, and its hope!

1900s, Address at Providence (1901)

1961, Berlin Crisis speech

On the issue of priority to internal development vis-a-vis external defense.
The Making of the Indian Atomic Bomb: Science, Secrecy and the Post-colonial State

1960s, Where Do We Go from Here: Chaos or Community? (1967)
Context: Nowhere have the riots won any concrete improvement such as have the organized protest demonstrations. When one tries to pin down advocates of violence as to what acts would be effective, the answers are blatantly illogical. Sometimes they talk of overthrowing racist state and local governments and they talk about guerrilla warfare. They fail to see that no internal revolution has ever succeeded in overthrowing a government by violence unless the government had already lost the allegiance and effective control of its armed forces. Anyone in his right mind knows that this will not happen in the United States. Furthermore, few, if any, violent revolutions have been successful unless the violent minority had the sympathy and support of the non-resisting majority.

Death and the Dervish (Derviš i smrt), Part II, page. 329.
Death and the Dervish (1966)

Presidential campaign (April 12, 2015 – 2016), Speech in Warren, Michigan (August 11, 2016)
Context: I will stop any trade deal that kills jobs or holds down wages – including the. I oppose it now, I’ll oppose it after the election, and I’ll oppose it as President.... I will stand up to China and anyone else who tries to take advantage of American workers and companies. And I’m going to ramp up enforcement by appointing, for the first time, a chief trade prosecutor, I will triple the number of enforcement officers, and when countries break the rules, we won't hesitate to impose targeted tariffs.

Statement https://fleuron.lib.cam.ac.uk/book/1079701600 to his constituents (14 September 1780) in the wake of the anti-Catholic Gordon Riots.
1780s