Yes, it all has to be done ahead of time, otherwise you're out of luck. For the same reasons that you can't write a will after you've already died.

Another good reason for trusts is to avoid probate when you die. Who wants your estate to be nibbled away by government and court fees and lawyers salaries. Not to mention the delays for your heirs. The goal is to move your assets into the trust, so that when you die you have very little that is outside of the trust. It is the stuff outside of the trust that might require probate. But if you get that down small enough, then there is no probate. This varies from state to state. I can't remember what the no-probate limit is here in Colorado where I am, but we are under it. It's like $60,000 or something like that.

People should talk to a lawyer specializing in estate planning in their state. You can protect lots of stuff in a trust. For example, say your kid gets married to a scumbag. After you die, having left money to your kid, you do not want said scumbag to get ahold of it should they divorce, etc. You can set all that up. You can also set up things so that your kids inheritance can't be touched by others trying to get money from them in a lawsuit. Or you can set up things so that your kids, in their moment of irresponsibility, can't wildly spend all their inheritance on video games. Rental properties you own should be put in LLC's, then into the trust, to protect you from a renter suing and trying to get at your other assets.

Lot's of good stuff in this area of estate planning. Worthwhile for many things, not just for the stranded overseas topic this thread is about.

If you're going the whole kit and kaboodle - a family trust, wills, various powers of attorney, HIPPA forms, living wills, resuscitation instructions, special setups to protect your kids, LLC's, etc. expect to spend a couple thousand dollars for a lawyer to set all that up. A simple trust would be cheaper, but the other stuff is important too, especially as you get older.