For comparison purposes, the UK rates on cap gains:

For gains on or before 22 June 2010, Capital Gains Tax is charged at a flat rate of 18 per cent.

The following Capital Gains Tax rates apply to gains after this date:

18 per cent and 28 per cent tax rates for individuals (the tax rate you use depends on the total amount of your taxable income, so you need to work this out first )
28 per cent for trustees or for personal representatives of someone who has died
10 per cent for gains qualifying for Entrepreneurs’ Relief

Further, there’s an annual exempt amount - the first ~10k is exempt from the tax (which basically exempts anyone but the top tax brackets from cap gains).

I’d love to see someone run the numbers to see how that system would shake out compared to the US cap gains, which is summarized in table form here. But it appears that the rates are comparable.