If you live overseas long enough, you can exempt a certain amount of income from your US taxes (it's close to $100k). If the country you're working in has a low or no income tax, that's almost definitely the way to go (plus it makes US tax time that much easier). You don't have to take the exemption though, and can simply count the overseas income as regular taxed income. If the country you live/work in has an equal or higher tax rate to the US, look into doing this; you won't be double-taxed (so if you paid $20k in taxes to the country you work in, and the US says you owe $15k, the US gives you credit for what was already paid so you end up paying $0; if you paid $15k and the US said you owed them $20k, then you'd have to pay them the $5k difference). It's more of a hassle, makes taxes more complicated, etc. However, with earned income, you're now eligible to contribute to a Roth IRA (assuming you don't make more than the income threshold). Might be eligible for some tax credits too, I dunno.
Oh, and just know that when you transfer US funds overseas, the other country's currency will be at an all-time high. When you go to transfer the foreign currency back to the US, then the USD will be at an all-time high. At least that was the case for us.