It’s not for free. It’s in return for being under the US security umbrella, which costs the US about $800 billion a year
Of course that umbrella could soon be gone, so it would be a moot point
Of that 800 billion, where is the money spent? If it goes to US military/industrial complex, it is basically a creator of US jobs.
So it doesn't cost the US anything.
The umbrella could already be gone. There are big question marks over how much the in-practice umbrella looks like the Ukraine war where the US State Department provokes something then Japan gets flattened in the crossfire. How much should they be paying for that?
People are coming out of the 90s mindset where the US was substantially more important than its competitors. It was easily worth paying for US protection then because it was obvious the US could back it up with muscle. Now the calculation is a lot less clear.