>Maybe the aliens are in contact with NASA/Government
If so, in't it much simpler for NASA to say to these aliens (who can travel between worlds easily), "Hey, don't fly in THIS specific spot during this specific time, by the way it's optical range for a shitty webcam on a fixed, predictable path, so like, it's really really tiny and SPACE IS BIG GUYS, just seriously avoid this tiny strip and you're fine."
That's like them saying, "Hey aliens, when you're visiting Earth and wandering around totally undisguised, try to avoid the front door NASA headquarters because we are filming a press release there today."
> The aliens might just be humoring the governments they're in contact with, they have no reason to hide from us or fear us
So now they're... just trolling us?
Space is big, so obviously, this is deliberate action. If they wanted to reveal themselves they wouldn't do so via a grainy image from the ISS; they could just appear over New York City and just hover for a while. If they wanted to hide, again, they could simply not be in this one specific spot at this one specific time.
> Space is big, observers are few, and non-official observers are easily discredited if something slips through
It's possible to discredit a few people, but with collaboration it becomes harder. I can concede an occasional independent voice may be silenced, but this kind of thing requires a competence that the US government has shown with literally no other part of its administration.
> The aliens might similarly be in contact with the other space-faring governments on the planet
That assumes that essentially the Chinese (current frenemies of the US), the EU (a group of many man disparate countries with plenty of quasi-rogue-state elements present), the Russians (traditional enemies of the US and relations are quite cold right now), the Indians (who are third-world aligned but lean toward Russia) would all agree to, under no circumstances, no matter how bad it got, no matter what, including things like the total collapse of the USSR which happened not all that long ago, or during heightened tensions such as Russia playing in the Syrian sandpit, or Russia invading Georgia, or Russia carving up the Ukraine, would never ever blab about this, ever.
It's the same problem with fake moon landings. The Russians had roughly equal instruments pointing toward the moon and tracked every US launch made there, and put their best minds to work analyzing it (for military purposes). If the landing was fake, they would laud this over the corrupt capitalist pig-dogs for all eternity, but even they acknowledge the US was really there.