Plenty countries to look at who do very well with different kinds of social assistance and minimum income. Of course all those countries don't spend 15% of their budget (actually roughly half of discretionary spending) on 'defense'. Which really is a form of social assistance as well at this point in the USA. In 2017 142.5 million US citizens were employed by the US military (1.3 million active duty members). That's the biggest social employment scheme ever seen.
It's not that simple. Most countries have just an amount that is a small help, which is not enough to pay for your mortgage, groceries, medical bills, utilities and gasoline. It is just a very small amount to maybe help you not to starve. Also usually it is paid only for unemployed people, people that can't work etc. Because if those countries wanted to pay a bigger amount, maybe let's say 1000-1500 dollars to everyone that can't work the burden would be absurd in the public budget, even for a country like US. Unless you just print money like crazy to support it which would bring other problems to the economy.
Small programs can definitely happen and work well, like it exists in Brazil and help poor people a lot, although is a very small amount only for people not to starve. Bigger programs with larger monthly payments is most likely doomed to not work and destroy a country's economy unless you have some very specific exceptions like Norway where they sovereign oil fund can probably support the population for centuries.
But if US wants to try it, go for it, it's always good to have someone serving as an example.
Also remember that one of the reasons US is so rich is because of it's power which is also supported by that absurd military spend. Of course it can be lower than that but rest assured US would be a totally different country without this spending.