Swiss banks were doing business in the US, setting up offices in the US, and literally counseling American clients on how to export their assets. These were Americans living in America doing business with Swiss banks on American soil in order to avoid taxes.

Several banks have been stomped on for this behavior, the "oldest bank in the world" closed as a result and there have been many other actions.

If you don't want to deal with American taxes, renounce your citizenship, or earn less than $100k abroad.