Snowden was granted a security clearance and he was entrusted with the country's secrets. You don't just run off to an adversarial country with those secrets where their intelligence services can get a hold of them and use them to endanger the lives of our troops and the lives of informants that we are using for national security purposes. It's not OK to do that when you are an American citizen, especially an American citizen who was trusted with a security clearance. If he had a conscience, he should have thought about the lives he would have and did endanger with his actions. Every government has secrets and secrets are needed to be kept for national security purposes. That's just a fact of life that will never go away.
He fled because he felt that his life was in danger. The government was probably not offering him protection at the time. He was definitely not America's sweetheart.
He blew the whistle because he realized he had all this intel on an illegal program. He wanted to end it. He needed to tell someone. And honestly, you cannot trust everyone. The government has corruption and had he stayed where he was, some agent could have eliminated him.
Here's a hypothetical situation. Suppose you were in the CIA. You were involved with a project that was eliminating people and claiming their assets to pay off the national debt. If one of the targets was one of your relatives, would you stay silent or would you leak? Then would you stay in the US and expect a congressman or politician to help you? Why should they help? Snowden realized this so he fended for himself and he looked outside the US for help.
I call the US home. But I do not approve of everything that goes on in this country. If something feels wrong, I cannot deny how I feel.