You're probably right, though U.S healthcare costs per capita are much higher than they need to be, and would be much lower in a "proper" single payer system like in Europe. In any case, a wealth tax would still help a lot with being able to fund these programs. Yes, the working class does have to pay as well, but it'd be much less if there were a reasonable wealth tax.

But yes, global co-operation to enable a large enough tax on wealth is not going to happen any time soon. A more likely scenario is that as automation develops and as the share of income that capital gets grows, the working class will end up in a position bad enough that capitalism will collapse and be replaced with something else. Hopefully with something better, but could also be worse.