Why are some light bulbs labeled “Not For Sale in the United States"?
Chances are that those bulbs were produced during the U.S. incandescent ban (2007-2019). I'd look for LED bulbs instead, for both cost and environmental reasons.

In 2014, the Department of Energy issued regulations that would extend the efficiency standards of the 2007 EISA law to some specialty bulbs, effective January 2020.[91] The new standards would apply to Edison, globe, and candelabra bulbs among others. In February 2019, the Department of Energy announced a proposal to withdraw this change. In September 2019 the Trump administration rolled-back these energy efficiency standards for lightbulbs with the Energy Department's publication of regulations in the Federal Register.[92][93] The Energy Department announced the reversal of the 2014 regulation that would have taken effect on January 1, 2020 and implemented the last round of energy-saving light bulb regulations outlined by the Energy Independence and Security Act of 2007.[94]
https://en.wikipedia.org/wiki/Phase-out_of_incandescent_light_bulbs#United_States