I'm surprised no one has commented on these lists as they may well offer a solution to where the regular US citizen, resident in the UK, should invest their after tax money. By regular I mean that you have a few bucks to invest and don't pay 30k GBP a year to HMRC to exclude foreign investments from UK tax or want to get into complicated tax avoidance planning structures . It includes a number of US mutual funds from big companies like Vanguard that are classed as distributing or reporting by HMRC, so the US expat who pays tax on an arising basis in the UK can put money into these without running foul of HMRC rules that tax capital gains as income on many offshore funds. They obviously also get around the US PFIC rules. I believe that the funds like Vanguard Wellesley that are on the list are in fact the US domiciled funds. But a call to check would be warranted before investing.
So the list of relatively simple efficient tax investments is growing, we have the following tax advantaged accounts:
UK cash ISA (NOT!!!!!!!!!!!!!!!!!!!!! stocks and shares ISA)
UK employer sponsored pensions
US ROTH and IRA
maybe UK Personal Pension Plans, opinions vary
taxable accounts, but dealt with sensibly and easily for UK/US taxation
US mutual fund that have HMRC distributor status.
Individual stocks, shares and bonds (but you have to be a good record keeper)