FBAR, FATCA and if you start a business, form 5471 and friends. I got some quotes from a few accountants and I will likely have to pay thousands of dollars for assistance just to fill out informational forms and pay (maybe) a few hundred dollars in US taxes.
Whether you are an American who moved to a treaty country, or a treaty country resident who moved to the US, it is not likely that you'll have to pay a lot of US taxes if at all. (The treaties I am familiar with are quite reasonable). However, unless you are a tax professional yourself, you are going to be "taxed" by a professional to prepare all those papers that you must file.
I know someone who moved to the US, and whose tax filing on one year topped 150 pages of "informational data" despite not having to pay one cent.
I have never met a person who is in any way familiar with the US tax code who thinks it is makes any sense or is reasonable. Only people who never had to really deal with it think so.
Also, if you don't plan on moving out of the country, which the majority of Americans (and probably citizens of most countries) don't.
(Not that the votes seem to matter - you get to choose which faction of the military-industrial faction gets a salary this year, but not anything of consequence)
Since the US nowadays puts so much pressure on Swiss banks most - if not all of them - are extremely reluctant to open bank accounts for US citizens.
Luxembourg and Lichtenstein will gladly take you money, though ;-)
http://www.letemps.ch/Page/Uuid/0a130fdc-238a-11e3-8a42-a451...
The US tax code, as evidenced by FBAR and FATCA, assumes that the only purpose of any financial transaction or account outside the US, is to hide money from the IRS. You have to report each and every "account", with contact details at the institution, every year, on two independent forms (similar yet different), as well as every transaction in securities (if you can actually do them anymore - most places won't even let you if they know you are paying taxes in the US).
If you are not a US taxpayer already and planning to do anything in the US, be sure to talk to a CPA that specializes in those kinds of things (preferably, one who is also familiar with the treaties and tax code in the country you are moving from). You need to do this both on the business front and the personal front, or you are likely to be seriously and horribly surprised one day.