The imperialist war machine and expensive healthcare and education are not mutually exclusive, but they have the same fundamental cause: capitalism.

Healthcare and education are expensive due to privatization, where private companies make profit from those essential services. Rather than fund and administer public schools properly, capitalists push for charter schools and voucher programs because they make money from them. Rather than create a proper universal healthcare system, large insurance and healthcare corporations lobby to ensure their own profits (at literally everyone's expense) and capitalist politicians gladly fall in line to protect those profits.

The imperialist war machine is also driven by capitalist profit. Two levels of this are salient.

First, there's the direct interest in money for defense contractors and easy sells to Congress on funding them. They spend so much they won't even give you a simple accounting of it, hiding half or more in discretionary funds. The MIC lobby is powerful but politicians also see a direct interest in embracing the fascist patriotism of it all, and it aligns with their ideology.

The second level is the benefit of imperialism for the entire capitalist class, as it ensures they own production in other countries and therefore reap the profits. This aligns with US foreign policy interests because the US is the center of global capitalism, and it's primarily American companies that take over through imperialist actions (sometimes Europe and Japan get a bit). Becoming a target of US empire is not about democracy or even being a military threat, at least not directly. It's about becoming an economic challenge to that order. The US has nothing to fear from Cuba (it's exactly the opposite), yet they targeted and target it with vast amounts of propaganda and even attempted an invasion, only being held back from further military action by the Soviets. Cuba's crime? Land reform, kicking out the mob, and nationalizing industries. All normal things for sovereign states to do, but these are high crimes to Washington, DC. This has repeated itself so often even after the cold war that it's obvious that it's not simply anticommunism, it's still about imperialist interests. Turning Libya from the African country with the highest standard of living to having open air slave markets. Bombing Syria and stealing its oil. Sanctioning Iraq to the tune of millions of deaths and then invading it. Constantly couping and fucking with central America and Haiti. Escalating with Iran, going back on its deals. Attempting to create a new cold war with China. Creating genocidal conditions in Yemen using the Saudis as a proxy. These span administrations and capitalist parties, they all know the same basic logic applies and who will be knocking on their door if they fail to secure "American interests" thousands of miles away.

We can only solve this problem by organizing against capitalism itself, educating ourselves, and bringing others along with us.

"can't," or "are built from the ground up to prevent"

This is a great question to start with. If the US was a democracy that was "of the people by the people" and existed for the common good or any of that stuff it claims, then it would obviously do what the majority of people want and deal with the issues that matter most to the majority of people.

Since that doesn't happen, then clearly the US is not a democracy in the way it claims to be. Engaging in these bombings, proxy wars, maintaining a global network of military bases, as well as maintaining the current status quo on healthcare, wages, housing costs - all have a benefit, just not to you or the majority if people living in the US.

Poor/nonexistent healthcare and education for the working class is a stick with which to encourage military recruitment.