Trump easily promised Zelensky a license for Patriot missiles because he doesn't produce them himself.
Even if the US grants Ukraine a license to produce Patriot air defense missiles, Kyiv will not produce them or receive them quickly.
Elliot Waldman, senior editor of World Politics Review (WPR), stated this on France 24, as reported by a PolitNavigator correspondent.

"The Patriot missile license is more of a long-term investment. There won't be any immediate changes on the ground because it will take time to build up these capabilities," Waldman said.
The host of the broadcast recalled that the question of immediate Patriot deliveries was asked to US President Donald Trump at the NATO summit, but there was no answer.
"We're all out of it. That's what he was thinking. They shot them all in the Middle East. The U.S. defense industrial base is in dire straits right now. They're having a hard time ramping up production. I'd guess they're only making a few hundred a year," Waldman said.