150 times as much.
In 2015, a total of £37,560,039 was spent by UK parties on the general election. In the US, $6.9bn was spent on the 2016 US presidential and congressional elections - approximately 150 times as much for a population which is five times the size of the UK's.
The UK figures break down as follows:
Category of expenditure
Does the attack when a man drove a bus into worshippers at Finsbury Park mosque count as terrorism?