With respect to defense budget, one of the reasons the US economy is so strong is because of its military. Since WWII America has expanded its sphere of influence to encompass the entire world and dating back to the Monroe doctrine has operated with a 'f--- around and find out' attitude, that only works if you have the military hence why so much is spent on force projection. As a result the US has relatively unfettered access to natural resources, favourable exports/trade policies, IP protection (e.g. semiconductor exports to China) and economic power (e.g. the petrodollar) which stems from being the biggest and baddest. It can certainly be argued to what extent we still need to be doing this, but its not as simple as 'spend less on defense', or your sanctions won't mean anything anymore and there will be far less incentive for foreign powers to act in ways that are favourable to American interests. I don't know the answer to this question but the discussions by foreign policy experts have led me to believe this is far more complicated than it seems.
With respect to healthcare efficiency, looking at $ spent/resident is overly inflated. All healthcare systems are terribly inefficient with different tradeoffs, absolutely agree that it needs improving, but it's also not as bad as the media would have you believe. Another reason the US spends so much is that the level of care for complex cases is also much higher than anywhere else in the world and almost all major medical advances and research comes out of the US. Looking at Canada we are at historic lows in research spending and there are countless treatments we do not offer.
In both of these scenarios it's also worth noting that a large chunk of both expenditures goes towards paying salaries (and most to non-executives), so 'spending' at face value is not necessarily 'bad'.