Nightfall is a good place to start a character. But an even faster method is to start in Factions, do the first 2 Canthan missions, run from the Marketplace to Kaineng Center, and then go to Nightfall and finish that campaign. Then come back to Factions and finish it as well. Oh, and as soon as you get to level 10, I suggest you go to the Eye of the North campaign just to get Vekk (Elementalist), Ogden (Monk), and Gwen (Mesmer) as heroes and then experiment with their builds (or just copy them from
PvX Wiki); but EotN is the most difficult campaign so you may want to save it for last. You will "finish" a campaign after you've done the last mission and you can not find any other "Primary Quest" in the respective campaign.
This may sound a little overwhelming but it will make more sense in the game. If you have a simple question, I suggest you search
the official GW Wiki. If you're still stuck, then feel free to ask right here
Using the American servers is a very good idea if you want to team up with other players. But, since you're still at the beginning of the game, you will probably be fine with henchmen or heroes. You can join a Pick-Up-Group later on, if you get stuck.
The Ranger is an excellent choice for learning the game but, in my opinion, they don't have many strong builds to choose from. Later on, when the game becomes more difficult, a caster profession like the Necromancer, Mesmer, or Ritualist would probably have an easier time getting things done. You should have at least 8 character slots so just try different profession and see which one you like most.
In the hands of a skilled player, any profession can accomplish anything. All that matters is how much effort are you willing to apply in order to understand the mechanics of the game.