If you assumed a similar per capita tax rate, but more government is required to deploy the taxes in a larger nation, the larger nation would presumably end up with less money deployed per capita.

Of course I am neither a social scientist, economist or political scientist.

People always like to rush to talk about economies of scale, completely forgetting that diseconomies of scale are also a thing.

(And even that's all assuming that you think Finland's demographics are comparable to the US's and that causes of homelessness and poverty in Finland are representative of the causes of homelessness and poverty in the US.)