I am planning a visit to the States in December.?

You are asking about the entire USA and I can't answer you since every state has it's own laws what is legal in Texas in not legal in New York, if it is legal in Arizona it is not legal in California and so on.

Regardless of our "loosey goosey" gun laws, as a foreigner visiting our shores, you wouldn't be allowed a gun permit.

No, of course not.

"I hear gun laws in the US are pretty loosey-goosey."

We hear that you're an ignorant chump.

Of course not. You wont be able to go through even your own border in that manner. You will be asked for the nature of your "visit, how long you plan to stay etc. Taking a firearm with you ( a loaded one at that) will be rather difficult to explain dont you think?

Any fire arm must come with proper documents, permits and licenses to carry and proper locks and storage. You must demonstrate safety precautions you have on hand for the firearms.your own criminal records or reasons to bring them with you.

I think you can, in the state of Colorado.

Of course not.It`s too far.....