Is the United States or any other...

Well, yes, but you may not be alive to find out the results of their efforts. Just this past March, Canadian astronomers used a radio telescope in Ukraine to transmit a greeting toward four specific stars similar to our Sun. Sun-like stars were chosen as targets because they are considered the most likely homes for life. The target stars are about 50 to 70 light-years from Earth. Therefore, the RSVP will have a long turnaround time — it will take more than a century for the message to get there and any reply to get back. This isn’t the first effort to make contact with other beings. NASA’s Pioneer and Voyager missions, which left Earth in the 1970s, carry information about human civilization, just in case the probes are intercepted by someone out there. The four probes, however, are now just barely to the edge of our solar system. Earth’s radio, television, and other communication signals also may alert other beings to our presence. Since the 1960s, scientists have been “listening” for signs of life through radio telescopes. So far, they haven’t detected any such signs.