We police the world because being the world police is fabulously profitable. You want to maintain the largest economy in the world? Well then you want to keep up the status quo of "you can do business between most countries, and can ship anything across the world for pennies per pound with near zero risk".
Arguably, the biggest beneficiary of the US Navy's protection of commercial shipping has been China.
Especially considering China doesn't pay for any of that protection.
Yet again it's the US explicitly spending money to keep someone dependent, similar to Russia's selling cheap gas to put economic pressure on the west.
China and the US really really really don't want to go to war, because even an unsteady "peace" between us is so goddamn profitable. But the US wants everyone to be able to sail by the Chinese coast without harassment, and China wants to own the entire sea north of Australia so.....
That "bigger" is bought, and has been every year. We could spend that money on other things: social welfare, health care, etc.
So, excusing Europe's inability to deliver mass military aid, when they've willingly underinvested in their defense industry and equipment for decades, rings a bit hollow.