I think that the Republic of Texas, if it did not join the United States, is likely, in 2004, to include OTL Texas, eastern New Mexico (E of Rio Grande), southeast Colorado (E of Rio Grande and S of Arkansas River), southern Oklahoma (incl. lands south of the Canadian [at maximum] and the panhandle).
It would have a population of say 25 - 30 million.
The military would be along the lines of OTL Poland, Canada, Australia, Spain, or the Netherlands. Maybe a small aircraft carrier (certainly not nuclear), 4 - 5 small submarines (like the Russian Kilo class), a sizable force of destroyers and frigates, a small Air Force with maybe 100 - 200 aircraft, a regular army with maybe 3 Infantry divisions, 1 - 2 armored brigades, 1 - 2 mech. infantry brigades, and a sizable force of reservists. A maximum military size for the RoT would be along the lines of Taiwan.
P.S. I know it's popular but George Bush could NOT be the President. He was born in CT.