Questions about the plot

I caught saw this turd on TV today and was sort of paying attention but not really. God it's so bad. Anyway I recall a scene where that Government guy (Galloway?) was telling Prime that if the president asked the Autobots to leave the planet would they honor that request. And then I thought wait, since when does America get to tell giant robots what to do? Aren't they on earth for a reason? Why doesn't Prime just tell the US gov to suck it and go seek asylum in Canada or something? And are the giant robots a big secret or not? How do you cover up a giant robot rumble in a major metropolitan area from the first film? This isn't like MIB where they can handwave it with a roofie laser. And if the Transformers are still secret to the rest of the world they why does the US operate in foreign airspace and waters with total impunity?