Coupled with the sheer volume of it's offshore banking, here are the reasons, USA is number one on that list, based on certain indicators.
- Banking secrecy
- Details of trusts don't go on public record
- It does not comply sufficiently with international regulatory requirements
- No requirement for for company accounts to be public record
- No requirement for beneficial ownership of companies to be on public record
- It doesn't maintain company ownership details in official records
- Doesn't participate in European Union Savings Tax Driective
- Does not have adequate access to banking info
- It allows company redomicilation
- It allows protected cell companies
All of that and it is estimated that the USA loses some $100 billion a year to it.