When my brother and I were growing up, our parents were adamant about taking us places both in Michigan and the US as a whole. In this way, I've been able to visit 22 states (although my goal, of course, is 50) and see a great deal of both peninsulas of my home state. It was, truly, an invaluable experience.
Some of you are going to disagree, I'm sure, emphasizing the wonders of traveling abroad. I've been to Canada, Mexico, the Netherlands, and Belgium, and I value those trips for many reasons. However, being an American writing in America about Americans, I find it essential to my fiction that I know America.
I used to write almost exclusively about suburban Detroit, because that was what I knew. Now I also write about rural, small-town North Carolina, having spent almost a decade living there. Boston/Cambridge will no doubt make appearances in the future, as well as other places I've seen and loved. It is unspeakably important that I am able to write clearly and accurately about these places; in choosing them as settings, I have made a commitment to the cities, their people, and potential readers to be as truthful as possible. Rendering a city incorrectly can alienate or even misinform your readers, and that wouldn't be cool.
Repeat excursions are, I think, equally important as the initial trips. For example, back in May, Mom, Dad, and I spent a long weekend in Harbor Springs, Michigan (across the Little Traverse Bay from Petoskey) and made a foray into Mackinaw City. I grew up visiting Mackinaw on a pretty regular basis, but it had been so long since I'd been that I couldn't have fleshed out certain details from memory if I'd been given a pop quiz. Now that I've had a refresher, though, I can consider using the place--and its landmarks that appeal to me most, such as Scalawags--in a story in the near future.
Ultimately, my point is this: I don't consider it to be isolationist when a person chooses to explore the beauty and offerings of our own backyard, which for you might mean your immediate geographic area but for someone else might mean our entire swath of North America. There's so much history to learn and so many really, truly awesome sights to see that it would be a shame not to do so, and an even bigger shame not to include them in your writing so that you might share them with others.