Spoiler PP3 ETS VERBAL

Why is option A correct? Which suggests this where exactly? Isn’t option A too generic to be assumed as a correct answer? I thought I was using outside knowledge for option A. I cannot figure out where is it inferred in the given passage. For all we know is that declaration has republican ideas. How can we be sure that such a declaration presents political ideas which US did not live up to?

@Leaderboard Could you please help?