"for the simple reason that US has no UK-style benefits system where you can keep having kids and state will give you a place to live, money to live on, etc."
You need to go see how the poor live in any large US city to get an idea of what you are talking about. It doesn't have to be the projects of Chicago or East LA or Watts or South Central. Any big US City and the poor in the rural South of all the south. The poor of New Orleans before Katrina.
one of the differences here is that we have to drive through a lot of the poor parts of Large UK cities to get to many of the cozy rich parts. With US cities you just take your certain Interstate exit and you never have to know of the huge areas of social deprivation equal to small British cities in some cases. Because largely their cities are planned and laid out for the most part, not growing organically like the British ones did over centuries.
I take it you are referring to some recent news (say in the last 5-10 yrs) reports out of some states now making benefit recipients 'work for food' and hunting down deadbeat dads to pay for all their kids etc.
Those laws are only coming into effect in the last 10 yrs or so in very few states and I can imagine being challenged in the courts so a lot of other states are playing a wait and see game.
These laws were taking hold in the long era of a very right of centre US Politics (including the entire Clinton era, btw). Deadbeat dads, teen pg, abortion, homelessness, benefits, HUD Homes (equivalent of Council homes) the abuse of crack cocaine in black communities and the abuse of methamphetamine in poor white communities, failure to complete high school in many demographical areas, Goodwill clothing depots... the list goes on.
There is little for either the UK or US to be proud of. Point for point, they match each other.
I agree that the US has a different mentality towards alcohol and the workplace but I think this comes out of a long history of an ambivalent relationship with alcohol, for example, the Prohibition.