You're missing the point, Thatcher was terrible and indeed part of the problem as far as the special relationship went, however she was also stubbornly driven to get her way with things regardless of opinion polls, focus groups and media reaction, traits that no other PM has had since her. That kind of "strength" of conviction is what would be required to break the status quo.
Major was blown around easily by the factions within his party, Blair was blown around by International relations, the media and factions within his party, Cameron seems to be easily blown around by media reaction and results of focus groups and straw polls. Thatcher was a stubborn bitch who reacted to opposition to her positions by being strengthened in her resolve rather than bending and moving in the way that all other PM's since her have been.
It is unfortunate that her positions were so despicable, because someone with her strength and resolve and conviction in her beliefs, tied to a more Liberal ideology would be an awesome PM for us to have, but we seem get weaksauce lapdogs instead.