The answer to “how do we pay for it?” isn’t to point to military spending, it’s to point to the fact that the US spends more on healthcare than any other developed nation. There is no evidence-based reason to believe that universal healthcare wouldn’t cost less than what America is doing now. Yes, people have their models and theories about why american healthcare is so expensive that would still exist under universal care, but that’s all they are, made up formulas and pet ideas and they all rely on the idea that universal healthcare would not be transformative (while simultaneously arguing it would be transformative in bad ways).
When someone says, “How would we pay for it?” ask them why they think it would cost more, considering it costs less in all known cases. The idea that it would cost money is conservative fairies and unicorns.