In some ways, the GOP's foreign policy is now better-intentioned than it was decades ago, and it just makes bigger messes. Since the end of the Cold War, we've been very gung-ho about democracy abroad, often without really understanding how the countries we're "liberating" actually work.
Democracy was not going to work in Iraq. It's an unstable country with a small middle class and ethnic and sectarian tensions that completely override any sense of national or economic identity. Instead of partitioning the country along said lines, which would probably have given us some measure of stability in at least Kurdistan, we imposed a system that we knew wouldn't work on a society that didn't want it (because real democracy means giving up your sectarian bickering- anyone can hold elections, but they're not the same thing).
Then, pretty much as soon as we left, Iraq collapsed, as it had been itching to do since we overthrew Saddam, and ISIS filled the power vacuum.
Why do Americans keep doing this? Because we think everyone is an American, yes, even Republicans when they're clear-minded enough not to indulge in bigoty. Everyone is an enlightened Westerner at heart; if we just remove the evil dictators and insurgents that oppress them, they'll put away their silly sectarian divisions and be part of a modern Western society. (I think part of the issue is that America is defined not by an ethnicity or sect but by the lack of any clear ethnic or sectarian identity. This is what makes America wonderful, but it means we don't understand why Iraqis insist on thinking along religious or ethnic lines.)
There's a case to be made that a bit more realpolitik could have saved us a lot of money and bloodshed. Instead of propping up impotent democracies in Baghdad or Kabul, Nixon or Eisenhower would just have put in better strongmen. They'd have maintained national stability at gunpoint, but if we're unwilling to redraw borders, is that actually worse than the very real alternative, where insurgencies maintain national instability at gunpoint while the federal government sits back and panics?