Buying iPhone X from US while not being a resident

Do you plan to purchase on line from US Apple online store or whilst visiting the US

Online ,Apple do not ship cross-border

and if a purchase in US at a store the decision is which model as I assume the X is not yet released in Egypt

iPhone - View countries with supported LTE networks - Apple

and then if unlocked iPhone X are available having gambled on the correct model

In addition to wegras's reply, you should note that the warranty would only be valid in the US, so you would have to travel back there or send it to a contact there if it ever needed to be repaired/replaced.