It’s different stuff. Ukraine isn’t equipped or trained to really get the benefits of modern US weapons. You can see this with the M1 tanks, we trained crews how to use them, but without the supporting doctrine and strategy from commanders they aren’t that useful. They also don’t really have the capability to do maintenance as effectively, basically every US vehicle requires absurd maintenance.
If the US really wanted to help Ukraine, making the country a no fly zone would probably be the biggest benefit.