Received a judgement by default... by cavalry portfolio... a debt collector service. Now they had a sheriff show up at my home due to a levy, and theyb assessed my assests. Can they do that?

Yes, you owed someone money, they sued you and you did not show up in court to fight it, ( and did not make any payment arrangements prior)

So they got a judgement, and can according to the law in your state do collectoin activities that are legal in your state.

Yes, FrChuck is right. You owe it, ignored the summons and now according to your state laws the default judgement takes effect. Bank levy garnishment of wages are likely to follow