No, the geography advantage holds true for any time frame since our borders are secured by our power and having only two bordering neighbors, both friendly. With the removal of territorial gain from the scenario that would leave a big open question as to why someone would want to attack us? Well there have been a few instances of interference with our shipping. These previous events would be unlikely to reoccur today but there always could be minor tensions here and there. Doubtful any would escalate into a full blown war though. Since we are the world's most powerful economy and the biggest market it is not advantageous for others to seek conflict and with the proven ability of our military it would also be suicidal, which is also bad for business. What then would be the most likely cause of future friction? The obvious answer is that our meddling could irritate others to the point that they strike out. Militant activism, contrary to popular notions does not increase security rather it invites tragedy.
Mexico is not a "friendly nation."
With the removal of territorial gain from the scenario that would leave a big open question as to why someone would want to attack us?
As far as nation-states are concerned, you're probably right. And if they did attack us, it would most certainly be in an unconventional manner meant to destroy us economically, not occupy us militarily. Of course fanatical terrorist orgs would have no other option than to attack us in this manner, and plenty of reasons to do so (none of them rational, however).
Militant activism, contrary to popular notions does not increase security rather it invites tragedy.
I'd imagine you're talking about pre-emptive military action here. And if you are, my reponse would be that sometimes it increases security and sometimes it doesn't. There are a number of variables to consider.