"True, free democracries" are not in US interests.
Of course they are. Inserting a pro-U.S. dictator might be beneficial in the short run, but in the long run it erodes any claim to moral superiority and repels potential allies and partners aside from useless weak dictators. Moreover, (actual) democracies tend to be better run and more effectual than dictatorships, meaning that they will grow to become more capable and useful partners over time. If you look at the actual Cold War, the countries which democratized or maintained democracies through the period were far more useful as allies than all the dictatorships that the CIA supported, which were mostly just useless resource drains that had to be continuously propped up instead of any kind of "asset".
More to the point, who is Panzer to decide what
the player thinks U.S. interests are? Maybe I
don't think that U.S. goals are best served by setting up expansive mandates or creating a colonial regime in Africa. Why should I
have to set them up if I happen to be a good player, instead of acting like I'm NATO in Libya in 2011, celebrating the defeat of the Nazis, and going home to let the Africans sort their own shit out? I mean, that offers plenty of opportunities for problems too, especially for South Africa but also for the United States--just
different problems than the mandates. Or an intermediate option, along the lines of what
@Konev1897 outlined, where you allow the locals to form their own states but force them to join OFN and its free trade zone. This could then generate a lot of problems down the line without being blatantly colonial the way that the mandates are (and would be much more similar to what the United States actually did during the Cold War)
I know some South Americans who would have... strong opinions about the US being portrayed as a completely benevolent and freedom-loving force, and I can't disagree.
Of course the United States should not be portrayed as
inevitably totally benevolent and freedom-loving. But besides the fact that it's opposing the actual
Nazis, not just Communists, the way things are set up completely denies player agency or the ability of the player to steer American policy in any direction other than the one the developers chose. As it stands, in
domestic policy the United States has a huge range of options--even leaving aside the Yockleys and Hall, since they basically destroy the country, you can arrange for anyone from a democratic socialist to an arch-segregationist to gain power and enact their favored policies. But then suddenly when it comes to foreign policy you only have right-wing options straight out of the Dulles brother playbook no matter who is actually running the country, no matter what you might think about their idiocy. It's a very jarring shift that really ruins the experience of playing as the United States.
It's also odd in light of the fact that supporting Free Indonesia works exactly like this, that is you support the libration movement, help them win, and then go home. You don't even get anything economically out of it, since Free Indonesia has closed economy and won't import rubber (so it's better for you if they
lose, in economic terms).