For context, the 2022 Defense Dept Budget is $752.9 Billion. $16.8 Billion is 2.2% of the annual defense budget.
Let's look at just some of what we got for that 2.2% of the annual defense budget.
1) Save a fledgling democracy, giving us a chance to stick up for our principles. This has united most Americans across the aisle, at a time when that has become incredibly rare.
2) Restores credibility of US intel agencies that had suffered badly since 2003.
3) Shows why NATO is critical. Until Russia invaded, the necessity of NATO was openly questioned publicly and frequently. Open Russian aggression reveals that NATO is absolutely critical to US and European stability.
4) Strengthens NATO. NATO gains Sweden and Finland and soon will be able to add Ukraine. That gives NATO 2 new bordering countries with Russia plus the ability to hinder the Russian Black Sea Fleet and completely bottle up the Russian Baltic Sea Fleet in port.
4) Destroys the bulk of the professional Russian army, along with their equipment. Also destroys the ability for Russia to replenish and rebuild that equipment, rendering Russia impotent for at least the next decade or so.
5) Shows that US equipment is utterly dominant versus Russian tech, which almost certainly also applies to Chinese tech. You want shit that works and works well? Buy USA.
6) Makes it much less likely China tries to take Taiwan by force. Even not even considering military aspects, their economy would be destroyed instantly by sanctions.
All that for 2.2% of the annual defense budget, $16.8 Billion. That's one of the best returns on investment in history.
Anyone criticizing the US sending aid to Ukraine does not have US strategic interests in mind.