Nope I can't see it happening main for reasons already stated, even if you could take the nuclear threat out of the argument the logistical difficulties alone would make such an event incredibly difficult.

To a large degree the same issues would apply to much of Europe and Russia, I suspect the days of large scale warfare between first world nations is pretty much over.

There is surely no need for an invasion, hardly any country exists which does not have undercover agents working in the USA. So please - just keep your eyes open.

That last option...

No - Honestly, I believe it is possible, but unlikely...
Then again, I'm no expert on this kind of stuff, and there are many factors to consider when thinking, realistically, about an invasion.

If there ever was one I would be on the front lines defending my country.

Won't happen in my lifetime, but I won't reject the possibility somewhere in the unforeseeable future, who knows what the world will be like in 100 years? Unless Navies become obsolete the United States won't really have anything to fear. 3,000 miles of ocean on one wide, 6,000 on the other and the world's most powerful navy making sure nobody gets antsy in those areas.

Originally Posted by Wolf

No - Honestly, I believe it is possible, but unlikely...

I will say - significant political and/or economical changes in the world are necessary to make ground invasion a real threat for US.

Any other threats/possible aggressors rather do not have enough resources (aircraft, vessels as well as modern enough weaponry) or their preparations for invasion certainly will be detected by the US intelligence (it is impossible is nowadays to conduct and prepare such operation against US-type country without being spotted from satellites or in other way of intelligence) and they will be preventively attacked.

Two Boomers alone would very effectively take away anywhere enemy forces call home. Then, really nasty things would happen to whatever is left of an invading force.

Originally Posted by Missileer

Two Boomers alone would very effectively take away anywhere enemy forces call home. Then, really nasty things would happen to whatever is left of an invading force.

Disputable... what if `invader's home` is a large, decentralized territory? In such case lot of nukes will be needed to destroy that `home`.

Originally Posted by Damien435

Won't happen in my lifetime, but I won't reject the possibility somewhere in the unforeseeable future, who knows what the world will be like in 100 years? Unless Navies become obsolete the United States won't really have anything to fear. 3,000 miles of ocean on one wide, 6,000 on the other and the world's most powerful navy making sure nobody gets antsy in those areas.

My point exactly. Also, Americans are armed. It would seem that the project would require a complete population wipe-out to leave an invader free to walk in later to nothing, and take over.

But of course, if there is one American is left - the invaders are dead! He- he.

Then the critics would complain - Boo! Play fair - he was hiding and crept up on us. What about the Geneva Convention? Take him to The Hague on war crimes.

Originally Posted by Del Boy

Also, Americans are armed. It would seem that the project would require a complete population wipe-out to leave an invader free to walk in later to nothing, and take over.

Well, the `armed Americans` won't be key factor keeping America from invading. For example - Chechens, Iraqis and Afghanis also were pretty well armed (national sport of Chechens - shooting competitions from LAWs ) but it didn't help them safe from invasion.

So the key factor will be both technical advantage (both satellite and missile technologies) and oceans which keeps potential invaders away from America...