This 2014 hearing held by the US Senate on Permanent investigations is very interesting.It features Senators Levin and McCain and includes discussion of tax evasion, Swiss banks, tax treaties, FATCA the Offshore Voluntary disclosure programs and more.

The logic of the United States is approximately this:

Homeland Americans use non-US bank accounts.

Americans abroad use non-US bank accounts.

Therefore, (but not acknowledging Americans abroad) both Homelanders and Americans abroad use non-US banks for the same (nefarious) reasons.