Why was texas a good place to train world war 1 troops?

Because it was large enough and had a lot  of  power

WORLD WAR I. Texans were interested in the events of World War I from the beginning of the conflict in Europe in August 1914, and with the sinking of the Lusitania in May 1915, a resolution was introduced into the Texas Senate asking that diplomatic relations between the United States and Germany be severed. Texans were further provoked by Germany's continuing attempts to stir up trouble on the Mexican border. The German motive was to involve Mexico in a war with the United States so that America would be diverted from her possible support of the Allies. Toward that end Germany encouraged the internal turmoil associated with President Venustiano Carranza, Gen. Victoriano Huerta, and Pancho (Francisco) Villa, all of whom were watched closely by the United States. Villa's raid on Columbus, New Mexico, in March 1916 brought on the punitive expedition of Gen. John J. Pershing and the call-up of the Texas National Guard. President Wilson was opposed to American intervention in the war until Germany sent what became known as the Zimmermann Letter, a secret telegram transmitted in code to the German ambassador in Washington for transmittal to the president of Mexico. 

To sum it up you’ll get in a lot of trouble and even some legal action can be taken