Canada

If I was Canadian I’d want my government to be handing out fpv drones like they were candy to train up my population to fight a modern conflict

Edit: also, ied building and placement training

Plus thousands of kilometres of wilderness border, built in disguise, cultural mastery, and lootable weapons all over the place.

Don’t worry, America. We’ll come to you too.

Sure, sure, great ideas there. National security being of utmost importance, let's also burn down all the trees within 50km of the border, replace them with poison ivy, and pre-emptively nuke the tar sands to remove one incentive to invade and show we're not afraid to use the power of the bomb.

Here is the thing. Ukraine has, or could easily within weeks have, nuclear capability (they were actually instrumental in developing Russia's nuclear capability, and they still have the infrastructure, knowledge, and skills) and that is actually to their detriment. It only promotes a 'first strike' mentality in the Russians.

The land border between Canada and the US is just too long for either side to defend.

But here is the thing. The only way the American army could have the resources to do it would be through the National Guard. American forces are spread too thin throughout the world. The National Guard is under the control of the individual state.

The biggest states would be well prepared to sign non-aggression treaties with Canada, meaning their National Guard could not be used. The individual States can not directly sign a treaty, but they CAN prevent their National Guard from participating. If Trump tried to take charge of them, it would for sure lead to a Constitutional Crisis. Since the Commander-in-Chief of the National Guard Units is the governor of each state, not the President, the troops are only answerable to the chain of command that ends at the state level. The individual states would have all the reason they need to secede. It would be civil war second inning in America. And some National Guard units have their own fighter jets and air bases.

That chaos is Canada's best bet for defense.

During WWII the soviets moved all their important factories to Siberia.

Maybe move at least one or two of your strategic assets more than 50 miles from the border?

Nukes? Canada needs to close the Eldritch horror gap.

Actually, just nukes would already do

I just see a lot of our military not being into invading Canada. There is a lot of gray space between aggressively applying 100% to a mission and outright desertion. As a person who's spent a career in the military - I don't really know about the infantry-based guys, but the people I served with are not simple order-following automatons - regardless of oathes to follow orders...doing the wrong thing is doing the wrong thing.

Maybe I'm out to lunch, but I'd bet there would suddenly be a lot of broken equipment, and a lot of injured personnel, along with a demand that the children of our political leadership, be among the first of the "cannon-fodder" and "bullet-cushions" to cross into "enemy" territory. I'd also bet that you could say goodbye to our all-volunteer military recruitment numbers. Logistics would likely be another nightmare, as our civilian population would likely have to be violently forced to allow the military use of the roads to transport themselves north. Unlike our previous military campaigns and wars, where Allied ports were made available to mass our troops and supplies, there would be no friendly ports outside our own borders.

I'm not saying it couldn't be done - our military is larger than the next 13 largest militaries combined, after all. I'm suggesting that between the troubles of invasions in themselves, we'd also be dealing with near civil war conditions within our own borders, massive resignations of key people, desertions & AWOLs, protests and civil disobedience, equipment sabotage, and voluntary military ascession falling off a cliff.

There are plenty of military members who would absolutely, with full faith and dedication, follow any order given to them. I'm sure that there are at least some members of our military who (for some reason) would love to invade Canada. But between the domestic troubles, the half-hearted effort of those who would appear to be participating, and the pain of going to war in the first place. Nah, trump is just sabre rattling....it won't happen.