While the first story ("100,000, BC") was mildly accepted, it was the introduction of the Daleks to the series in the second story that cemented it's reputation, like it or not, as an established part of British popular culture. It was the party guest that refused to leave, quite simply because the attendees wouldn't let it. The BBC, though, had different intentions, but more on that later on.
In 1975, in an agreement between the BBC and the US syndicator Time-Life Television, selected BBC series were broadcast in the US- "Doctor Who" being one of them. Certain stories with Jon Pertwee as the Doctor from his first three years were packaged, but to very little success, as all of these stories were sold in episodic form and stations running them didn't broadcast them in transmission order. Just imagine. as Jon Pertwee had said it in 1987, seeing part one of "Inferno" on a Saturday afternoon, a baseball game at the same time the next week, and then only to return with part four of "The Silurians". Confusing, isn't it?
Some three years later, "Doctor Who" returned to the US, this time with Tom Baker in the role as his first four seasons amounted to 98 episodes, the exact amount needed to fill out a syndication order that included two other series. Tom's Aquarian outlook and childlike quality, combined with the popularity of the anti-hero archetype made famous at the time by Alan Alda as Hawkeye Pierce in the television series "MASH," made this attempt at the series in America a hit. Commercial and Public Broadcasting stations in the US picked up the show to a tremendous response, thus cementing the Doctor in America- 25 years ago.