Under President Obama and the Democrats, the pubbies have made a comeback in many suburban areas of the country that they have lost influence in over the past 20 years. For example in VA, the GOP pretty much lost NOVA from 2001-2009 for a variety of factors demographic change and urbanization not least among them on the local, state, and President level. All of which accumulated in the elections of Jim Webb to the Senate and Obama carrying the state in 2008.
However much of the Republican Party nationwide has adjusted to the circumstances, for instance by running candidates with wide appeal with roots in suburbia like Bob McDonnell in 2009. Additionally, since 2009 many of the suburbia NOVA voters who moved towards the Dems under Bush are going back to the GOP in droves because of the policies put forth by the Democrats and the fact that Obama has turned out to be something that he is showing that he isn't is the feeling at the moment. This in NOVA is leading to a graudal rollback of the Democratic gains over the past 10 years(the local and state elections coming up next week here look like they maybe a disaster for the Democrats), and it is looking increasingly likely that a suburbia heavy state like VA will go back to the GOP in 2012.
These trends aren't only being seen in NOVA, but other Suburban areas like chunks of Florida, New Hampshire, NJ, or the Philly Suburbs. With the Republicans putting forth candidates like Chris Christie Scott Brown, and Marco Rubio whose polices appeal to these types of voters.
Most of your examples took place in midterm, or off year elections.
1) Republicans have an advantage in most off year/midterm elections because many members of the democratic base (young people, the poor, minorities) don't show up to vote. And even then, many of these counties like Bucks and Chester weren't exactly blowouts for the GOP. Meg Whitman and Carly Fiorina didn't quite dominate the suburbs in California either.
2) State GOP candidates have more freedom to appeal to the GOP base in their respective states. Republican candidates in Pennsylvania, California and Illinois were able to soften their message to GOP or swing suburban voters in those states. In the general, the Republican candidate, whoever he or she may be, won't have that freedom. They will need to tow the party line and move to the right in order to secure the votes of the religious right and rural voters, since they're running a nationwide campaign.
3) Reagan and Bush were elected in landslides but their electoral strength rested on a tightrope. They simultaneously tried to please the old republican base (the affluent suburbs) and the new base (the rural religious right) but these are two entirely different voter blocks. It's kind of like the democrats trying to court southern whites and southern blacks, they were just too different to be in the same coalition.