How Much Would European Armies Suffer If The US Switched Off Their Weapons?

Despite that the United States has said it is resuming the flow of arms and intelligence-sharing with Ukraine this week, Europe is still alarmed and scrambling to figure out ways to make up for the potential future sudden absence of the single biggest contributor to Ukraine's defense. Washington is also by far the biggest supplier of weapons systems to European allies broadly.

If President Trump decides again to switch off the arms, or even begins withholding weapons and vital system components from NATO amid continued US frustration over countries not shouldering their fair share of defense spending (there's even been speculation/rumors of a Trump pullout from NATO), how quickly would European armies and economies feel the pain?

And as countries like Germany attempt a complete overhaul of their armed forces, which includes mulling plans for a trillion dollar dramatic restart to its defense industrial sector and infrastructure, how easy would it be for Europe to wean off American defense exports?