Regarding your questions:
1. No, an observer's longitude within a general given region will not matter. The comet's visibility is governed by its proximity to the Sun.
2. Best observing sites would favor the American Southwest, where the probability of clear skies is highest and light pollution less thanmost other places. The end of November and early December also often sees generally unsettled weather conditions across much of the remaining regions in the U.S., particularly the Northwest and Eastern sections.
3. No, before the comet disappears into the morning twilight late in November the Milky Way is situated within the twilight. During early December once the comet has reappeared, it will be rapidly moving up and away from any of the brighter portions of the Milky Way, which will still be situated very low in the sky and largely lost in the morning twilight. The same general situation prevails in the evenings after sunset.