As a percentage of the GDP (gross domestic product), we are spending much less than we spent during WWII or other major conflicts. And today, we're doing a lot more technologically with less money. We've become much more efficient through technology.
The US economy is also extremely resilient. The 9/11 surprise attack was meant to destroy the symbol of our economy and the economy with it. But it didn't.
Israel faces random acts of violence all the time (much more so than we do) and their economy has not collapsed.