My father inherited land in Mexico. All of my fathers siblings have since passed away, the land was divided by each sibling family. As an American can I legally claim it?

The answer is yes. But how to claim it can be a little complicated depending on where the land is located. You may own it outright or you may have to create a trust to claim ownership. This page explains it in long fashion.

Ref:

Foreign Ownership of Property in Mexico (http://www.blueroadrunner.com/ownprop.htm)