The short answer to your question is:
No, there are no jurisdictions anywhere in the world that can be considered “conducive” to trading for an American expat.
Relocating to a foreign country and establishing legal residency there is not the problem.
Money transfer to and from the US is problem #1, and opening a bank account in your new country of residency is problem #2.
If (1) you can’t move your US funds directly to an offshore broker, and (2) you can’t move your US funds to a foreign bank, you can’t readily fund a trading account in your new country, regardless of whether brokers in your new country welcome American expats.
I invite you to check out this thread – Going offshore to escape the CFTC
Most of the participants in our Offshore Broker thread are not expats – rather, we are US residents, attempting to trade peacefully with offshore brokers who offer us better trading conditions than the two (count 'em, two) US brokers we have available here.
The CFTC – the Nanny Regulator of Commodities and Forex – is intent on cutting off our access to offshore brokers, as part of their larger goal of completely destroying over-the-counter (off-exchange) forex trading, first in the US and then worldwide.
For the past two years, or so, the CFTC’s primary tactic in this war has been to attack the money transfer pathways between US traders and offshore banks and brokers. You can read quite a lot about this in our thread.
You might be especially interested in what two of our members have to say about establishing financial accounts in foreign countries –
The member who uses the screen-name MrInvisible is one who does have first-hand experience with the sort of expat issues you are inquiring about. Maybe he will chime in here with some information you can use.