Why is Trump spending any time on NATO? Why did he jam it into his speech? Most Americans are supportive of NATO and of the United States in the alliance, so playing up the hard bargaining/protection racket stuff is not going to win votes from the majority of Americans.
Well, it fits a broader pattern which then needs explaining: the RNC convention was narrow-casting, playing to those who are already Trump fans and not trying to broaden his appeal. There was no effort in any of the four days to appeal to independents, moderates, and disaffected Democrats except for token appeals to Bernie fans (which Bernie swatted away via twitter).
I have two guesses about this: (a) Trump thinks that what worked for the primaries works in the general election; and/or (b) Trump thinks he does not need to get more votes beyond his base, but just simply get more of his base to turn out.
Regarding (a), Trump is such an amateur and his organization is small, thin, and mostly full of people who would never make a regular campaign's A team that they may think that the primaries and the general election are the same thing. They aren't. Getting pluralities in a 3-15 candidate race against people who don't want to offend one's base is one thing; getting pluralities in 50 states simultaneously (or whatever number of states gets one to 270 electoral votes) against one committed, organized candidate who can ignore/disparage/attack your base is something else entirely.
Regarding (b), I am flummoxed why Trump might think that he could get so many more disaffected whites (mostly male) to do much better than Romney in order to overcome alienating so many more "sub-groups" as Steve King put it. Is Trump thinking that #voterfraudfraud will be so successful that getting historically low %'s of African-American and Latino-American votes will not matter? Given recent court decisions, that would be a bad bet. The numbers I have seen (thanks to my tweeps) indicate that Trump cannot win by just mobilizing a few more million white folks if HRC does as well as among minorities as Obama did. Given Trump's awful stances on all these groups, she should do fine with them.
Oh, and the magical thinking of more turnout runs into a real problem: turnout requires organization and teamwork. Having his campaign manager attack the Governor of Ohio means losing the networks and organization of the establishment in one of the most critical swing states. Who is going to beat the bushes to get rural voters (who are, by definition, dispersed) for the Trump Campaign? Oh, and alienating the Colorado delegation on the first day of the convention also cuts against the strategy of mobilizing more folks, as I doubt that the Colorado folks will be helping turn out Republicans for the candidate that crapped on them.
So, either way, Trump's decision to focus just on his base is going to bite him in a big way. Which is good for me as I see my role in talking down my Democratic friends and non-Americans over the next four months. Yes, we should not be complacent about the darkness that Trump would bring and there is some risk of him winning, but we should not panic either. Trump is the man of fear and desperation, ceding optimism (a basic American approach) and hope to HRC and the Democrats.