Odd if they don't have phone manuals available at the Samsung web.

The key I believe is if the phone is SIM-locked. If it was an operator
subsidised phone, then it most certainly is locked for SIM cards from this
operator only (after some specific time, the operators should support
unlocking the phone). It would be simplest to find out this by inserting a
SIM card from another operator (US or from Israel).

In order to use the phone elsewhere, or in Israel on a different operator,
one would need a subscription (SIM card) from this operator. Don't know the
case for Israel but pre-pay cards are often available, normally also monthly
subscriptions (post-pay) without a subsidised phone (although I understand
the latter being most popular in US).

If Cellcom has a roaming agreement with one of the US GSM operators (mainly
Cingular or T-mobile), you would be able to use this phone with the current
SIM. Calls may be a bit costly though but for a short trip this could still
be the cheapest option.

The title reads "world phone", I interpret this meaning it is a quad band
GSM phone. In the US you would need at least GSM 1900 support, preferably
also GSM 850. A quad band phone would have those in addition to the
frequencies used in Israel (don't remember if that was some sort of a
mixture of US and Euro frequencies).

US GSM phones operate at 1900Mhz and/or 850Mhz
850Mz is relatively recent.
The world outside North America is 900/1800Mhz.

If it is a Triband or Quadband phone, it will work.
If it is a dual band, it won't.