Mexico did not hold Texas for 200 years. Mexico wasn't even a nation until 1820, or so, and lost Texas in 1836. *SPAIN* held most of what is the current US Southwest, although they later sold parts of that to France, which we acquired by the Louisiana Purchase. Spain never included those terriories into what they eventually recognized as an independent Mexico back then, and we should not today.
For what it's worth while both Spain, and later Mexico made these territorial claims, they never truly cemented them, and thus, lost them...
the infowarrior
Thanks for adding to my knowledge of history.