The reason that the Space Force was viewed negatively is that it was completely unnecessary. The USAF was already handling space issues, and we did not need to add a new bureaucracy and chain of command to handle this aspect of the Air Force.

I loved Star Trek, but I also realized that it was just a fun fantasy, and that it will never be possible for living creatures (humans or otherwise) to travel from galaxy to galaxy in intergalactic space. You are correct that the show implanted the concept into the minds of the general public that there are many advanced civilizations in all parts of the Universe, and that it will be possible to visit them. There may, or may not be other advanced civilizations in the Universe alive at the same time, but one will never visit another unless they happen to be in the same solar system.