I think you're referencing an earlier era. In 1998, 42% of US households had at least 1 computer, 26% with Internet access. https://www.census.gov/content/dam/Census/library/publicatio...
In addition, and popular for a while, was pay-per-minute access where the ISP didn't charge the customer directly, but took part of the phone call cost. I don't know if this method of payment to an ISP existed in the USA.
That far fewer (only 9%) of British households had Internet access was probably more related to the cost of the computer and modem, and the country generally having less wealth than the USA.