How much do you really end up paying in US taxes? I understand that it will depend on how much you make, but it isn't as high as when you live in the States, right?
If you're talking
only of US taxes, it's more than likely the US tax bill will be considerably less if you're living and paying tax in the UK versus living in the US. Although there are no hard and fast rules.
If you're talking
worldwide tax paid (to both the US and the UK) the sum total of all taxes paid on a given amount of income will more than likely be higher than if you were living in the US and only paying taxes in the US on the same amount of income.
Everything depends on the type and amount of income.
Someone with
only $95,000 earned income in the UK with an additional $5,000 of interest from a regular high street savings account filing MFS will likely pay no tax to the US.
Someone with
only $12,000 unearned income in the UK with an additional $2,000 of interest from a cash ISA account filing MFS will likely pay a small amount of tax to the US.