Highly unlikely but not impossible by any means. $1 trillion is about 5.5% of the US GDP. In 2017 the US defense budget is about $600 Billion or 3.5 % of GDP ($18 Trillion). Yet it spiked at 22 percent in World War I. It spiked at 41 percent in World War II, and again at nearly 15 percent of GDP during the Korean War. So it’s entirely possible that in an emergency situation the US defense budget will actually exceed $1 Trillion.
Image credit: http://www.usgovernmentspending.com/defense_spending