If all space agencies in the world were in on the conspiracy, you would think there would be at least one leak, like Edward Snowden. There hasn't. Flat Earth is one of the dumbest conspiracy theories in the world.

I registered on this site to ask this but you seem to have already said it. What of all the space agencies that aren't NASA? Why didn't the Russians try to call the USA out when they claimed to land on the moon? Why do so many countries (many of which have a lot of reasons to resent the US) have their own space agencies, and not one has said that NASA/the USA are lying? How do private firms such as SpaceX exist? Is Elon Musk, a private businessman with no political ties to the US government, being funded by NASA to keep quiet about this conspiracy? Is he spending millions of his own hard-earned money just to fool us for no discernable reason? For instance, take a look at this footage released recently.
http://www.theverge.com/2016/5/27/11804110/watch-spacex-falcon-9-landing-onboard-video
Is this video doctored? If so, how/why? What do SpaceX, a private company that has nothing to gain by just lying to people without selling them something, have at stake to fabricate this? Do you have any proof to suggest this other than "the Earth is flat, thus this video cannot exist"? Why does your initial premise of the Earth being flat take precedence over all other evidence, and why do you try to bend all evidence to the contrary to support your hypothesis in such an ad-hoc way?