Sand can be used for glass.
In 1821, William Becknell led a wagon train from Independence, Missouri, to Santa Fe, New Mexico. The wagon train led by William Becknell then established a <span> route for international trade with Mexico.</span>
After the collapse it become a "democratic" nation so US saw it as less of a enemy. Also, it become a lot weaker so it wasn't as big of a rival or threat to the USA. Allowing it to trade and work together on major projects.