How do you propose we win a war against people like that?
It took not one, but TWO atomic bombs to force a surrender. Tokyo was prepared to fight to the last person. The only way to win that war was to bomb them into oblivion. That was a choice the Japanese made. The Japanese military engaged in unimaginable atrocities and despite being nearly annihilated militarily, they continued to fight. How do you stop an empire with absolute zero regard for humanity? The Japanese has plenty of opportunities to surrender but they kept fighting and fighting and fighting.
As far as America's military budget, the raw numbers are irrelevant, what is relevant is percentage of GDP. The US ranks 11th in the world at 3.3% with 18 countries at 2% or higher. So the "half a trillion" hyperbole is silly. The US also spends a half trillion on government-funded R&D spending and spends a higher percentage (and raw amount) than the entire EU. The US also is ranked number 2 in spending on renewable energy. The US also spends more on swimming pools, airports, and education than any other country. They spend more in health care than anyone else as well.
My point, citing half a trillion as some kind of outrageous amount is ridiculous given the US GDP is $18 TRILLION per year. The US also ranks 18th in the world on per capita GDP behind such countries such as Luxembourg, Ireland, Monaco and Brunei.
The US military is highly visible and obviously subject to a lot of criticism, but how many people talk about the French Army's frequent and continual adventures in Africa? France has forward deployed troops all across sub-Saharan Africa. How about the British Army in the Baltics and Poland? The British Army in Kenya and Sierra Leon?
It's fair enough to debate military tactics, however acting like the United States is some kind of military outlier just isn't supported by the facts. On a per capita basis and as a percentage of GDP, the US military isn't all that remarkable in terms of expenditures.