The better question might be what you define as nation building. Because you're stretching it to encompass everything from actual occupations and democratic transitions to random US-backed dictators that erode civil society and by extension nation building.
For example, the Philippines and Indonesia were both coherent nation states before the US intervened more heavily, and neither was ever in real danger of falling to commies or whatever the worse outcome you're implying. Sukarno was an effective nation builder where Suharto sucked at it, and Marco was plainly holding back the actual development of modern civil society in his country.
The bolded part doesn't make much sense. You're retconning history here and using hindsight. If South Korea was a success because it developed into a functioning democracy, despite US attempts to fight this, then that means Singapore was a failure in nation building for the UK since it never developed into an actual democracy. You're essentially giving the US credit for South Korea democratizing because the dictators the US installed were so incompetent they caused popular revolts.
I left South Korea off the original list because it was intervention in civil war, rather than a more explicit invasion to institute regime change and nation build. Although it was a toss up, because the same argument could be made for South Vietnam.
Regardless, in the wake of the war the US was involved in extensive nation building through massive civil and military aid, alongside the provision of security. Without which, the rapid industrialisation wouldn't have been possible. Not to overlook the US role in the war, although in itself that's not "nation building", the post-war efforts were very similar to those of WWII.
Overall, while the US can't be credited with the extent of South Korean success, you can't list it with categorical US failures like Iraq, Iran or Afghanistan.
The US enabled Marcos' infrastructure spending and PPP which, despite the ridiculous corruption and waste, did still manage to develop the country.
Likewise Moro and Communist threats were stifled, although obviously the sheer scale of corruption and lack of independent legal process eventually outweighed early success.
It would be argued as an overall failure due to the human rights abuses and sheer scope of corruption, but that initial "Nation Building" infrastructure and PPP did in fact develop the Philippines faster than was likely to happen otherwise.
Indonesia was always in danger of going Islamist (although the role of the US in Saudi influence is hardly blame free), and while the "Domino Effect" was bullshit, the secular, western, capitalist influence of Suharto's regime (not least the institution of the UDP) did in fact hold off both Islamist and communist influences, and established a stronger national identity. Again, the human rights abuses and sheer corruption make a good argument for it as a failure, but his implementation of US trained technocrats and US led involvement of foreign capital (including rejoining the IMF and World Bank) really did lead to economic development (industrialisation, education, infrastructure and healthcare) it otherwise would have been unlikely to achieve. Suharto doesn't have to be Sukarno for the US support to be seen as "nation building" or a limited success.
I'm not looking at "nation building" actions as a success just based on the health of a democracy explicitly implemented by a foreign nation. I'm looking at it based on the resulting demographic metrics (health, education, employment, income, gdp), political stability and infrastructure development. Which is why South Korea would be a success and Iraq is a failure.