They’re the poorest because the welfare state in the US isn’t as propped up by male tax payers as the socialist democratic countries of Europe. Also because there fiscal limits to how much funding you can give single mothers without disrupting the economic balancing act for governments. But welfare spending will increase as feminists succeed in mobilising female voters to vote for more welfare transfer from men to the increasing proportion of women who are becoming single mothers . Most major parties will comply because women are the most powerful voting bloc in the west. Every decade has seen single mother welfare increase in many parts of the west for this reason. Also as I understand in the US, welfare programs enable single women to purchase basic needs, but they would still need to work to provide for her children. But I don’t think it would be possible for single mothers to wholly provide for her children without government, even if welfare spending in the US isn’t as high as Europe or in Australia. It does enable women to be unmarried single mothers.