[chii]

why should US taxpayers subsidize a service for which non-US citizens could get a benefit from without paying any taxes?

"The gov't should pay for it" is not a solution to private problems.

[Y_Y]

> why should US taxpayers subsidize a service for which non-US citizens could get a benefit from without paying any taxes?

Because US citizens would benefit? Preventing outsiders from incidentally benefiting isn't a constitutional mandate (yet).

Would you oppose an anti-pollution measure even though it would also provide cleaner air to neighbouring countries?