Compared to many other countries, the US operates very differently in its legal system and legal aid. The US is a common law system with both state and federal statutes providing civil and criminal law. Civil legal aid and indigent public defense (criminal defense) are separate systems. There is no national legal aid budget.
This Current Overview section summarizes the current situation in the US. Some of this was written for international visitors to understand the US. It may also be useful to Americans who need a brief summary.