Are other countries plotting war against the US?

I don't blame the US for being paranoid and always wanting to investigate into other countries new advancements in technology. If we wan to keep our freedom, we have to be paranoid and make sure everyone likes us. But with Iran building secret nuclear facilities and keeping themselves secret about it, with the Chinese building a lot of new army advancements and North Korea and Iran brainwashing its people to thinking America is the devil and all that, I'm actually quite scared. Why are other countries doing this and being so secret but BUILDING UP there military. I wonder if everyone is going to secretly work against America. If the Muslim brotherhood get's to Egypt and manipulates the people (they could say America was friends with Mubarak and wanted this to happen to the people, just lies) and turn our ally, Egypt against us, were pretty much toast. What do you think? And do you think America will last another 20 years?