Learning a language without visiting a country is feasible, though it might be not as interesting as learning it inside a county. My learning went much better after I'd visit the UK. Travelling actualised many passive words sleeping in my vocabulary, helped to understand whys and hows of the language. I had had a good level of English before I went there and it made the experience much better. The time was absolutely right for the trip and the only thing I regret is too short time spent there.

First of all, a language is way too much about a culture, not only rules and exceptions. I see languages as systems, that have been whetted with time and cultures. Second of all, visiting "the country" exposes every hidden problem that haven't been noticed before. Therefore, you become to understand what you have to work on.

Because traditional methods don't work, and that's what you get out of country. But being in-country is not ideal either, because you cannot understand much of what's going on. You'll make faster progress as a beginner or intermediate doing lessons here, if you can find a native or fluent speaker who can provide you with 100% language you can understand. Google "comprehensible input". That's what you're looking for.