Hello, I am Keith, one of the experts on Just Answer, and pleased to be able to help you with your question.
The UK has a Double Taxation Treaty with the US which in basic terms precludes the same income streams being taxed in both jurisdictions. This is achieved by means of tax credits, the tax paid in one country being allowed as tax credit against the liability in the other country on the same income stream. The Treaty does not protect against differences in rates of taxation. The UK also has similar treaties between some individual states within the Union also.
You can find the Treaty here:
As far as the States are concerned it applies to Federal Income Tax and certain Federal excise duties. The UK it embraces Income Tax, Capital Gains Tax, Corporation Tax and Petroleum Revenue Tax.
I do hope that you have found my reply of assistance.
Thank you for your support.