Since SG has better health care, education, and infrastructure than the US, and also doesn't invade other countries or spy massively on its own citizens, I think it's fair to say that 22% extra of GDP that the US taxes its citizens is simply squandered.

This is just plain wrong. Mostly because Singapore and the US are different countries in different circumstances. Just to name one, Singapore is tiny. Things are a lot cheaper when you're small. Small countries are sustainable because international trade means you don't have to be self-sufficient, and because alliances with larger countries let you get away with having a weak military. The existence of large countries is pretty important for this dynamic.

Now, I'm not saying the US is doing a better job than Singapore. In fact, I think Singapore is probably using its money better, albeit for unrelated reasons. I'm just saying that your analysis is far too simple to be at all useful except perhaps by accident.