Aliens mistake a stuck-up, self-centred actor for Earth’s leader due to his popularity on social media. Placed on trail, he must prove the human race is humble and altruistic before Earth is destroyed to make way for a interstellar highway.

Here is an alternate version, which hopefully better illustrates the external goal.

Aliens mistake a stuck-up, self-centred actor for Earth's leader due to his popularity on social media. Placed on trail, he must prove the human race is humble and altruistic otherwise Earth will be destroyed to make way for a inter-stellar highway.

What Richiev said. The achievement of an external goal -- the "A" story -- can be a means to an end, the fulfillment of an internal goal -- the "B" story -- but loglines focus on the "A" story.

In a story, many times there are internal goals and External goals.

Your logline is focusing on the internal goal (Now he's forced to put others first) instead of the external goal. ("He must discover a secret death-ray and defeat the aliens" for instance)

I think loglines work better if you concentrate on the external goal (What he must actually must do to defeat the aliens) Instead of the internal goal (Become a more compassionate person)

Hope that helped, good luck with this!