Asked about the US-UK extradition treaty which has been described as "one-sided", Attorney General Dominic Grieve QC said there were "underlying fundamental problems that are not very easy to address".
"I think there's a lack of public confidence in the US justice system," he said.
There were perceptions in Britain that the US justice and penal systems were "harsh and disproportionate", leaving Britons "uneasy and uncertain", he added.
He told the MPs these concerns were "not readily curable".
More top news
Spurs say they are supporting troubled former star Paul Gascoigne after it was reported he had been placed on an emergency three-day detox.
A British jihadi from Portsmouth has been killed fighting in the Syrian Kurdish town of Kobani, currently besieged by Islamic State.
Russell Brand has criticised Newsnight presenter Evan Davis as "insidious" and "rude" following vilification of the star's recent appearance