The American arsenal.?

Well the stealth helicopter used in the Osama raid is really cool! I have looked into it alot, cause it interested me as well, its pretty secret still, but it was a stealth modified black hawk for sure. As for rail guns, they are still in development. They work, but they are still in development, many countries are developing them, but they are far from being put into active service. There doesn't seem to be any real clear counter to china's new ship and carrier sinking missile, but for decades the US and ally's have been working at anti missile systems. There are some working prototypes, developed with Israel to counter rocket strikes. Some of these prototypes heat the missiles to fracture, very cool, and there were plans to put them in the nose of a Boeing 747, i doubt that's still going to happen.

There are tons of weapons in secret development, but if we knew about them it wouldn't be so secret would it.

Are rail guns already aboard American Cruisers and Destroyers? No.

Do we already have a hypersonic stealth cruise missile that if necessary can be mass-produced in a short time if need be to say take on Chinese defenses? Also no.

Might we already have an answer to that pesky Chinese anti-ship ballistic missile? We did a long time ago.

No, rail guns aren't on US warships. Naval research and development expects it to be ready by 2020. They're trying to create a system that can withstand the heat produced by the launching of projectiles. Although, they do have laser type devices, I believe free-electron lasers, aboard several warships that are being tested.

We don't have hypersonic cruise missiles but we have hypersonic ballistic missiles.

The DF-21 isn't all that. It may be able to take out a ship, but in order to take out a carrier it would have to get past numerous other ships in the carrier battle group that could launch intercepting missiles.

Most military helicopters can be rigged for stealth missions, nothing special about it. Rail Guns are in development in loads of nations, other than that what you have is what you got

The chopper used in the Osama raid was either a modified Black Hawk or Osprary

We have some pretty neat stuff, can't say I really know all of it, and some of it that I've seen I'm probably not privy to tell, but the US is still top notch on military research and development. Can't say I've seen much in the weaponry department aside from your generic bang and boom type weapons, but who knows.

I know we developed a hover tank in the early 1990's....

We have some crazy stuff man, trust me I know.

If we do, we dont really want our enemies knowing all about it now do we?