I got rid of it years ago, thankfully, but I've heard the talk. As it stands, we wouldn't make it a week outside of a guerrilla war, and I don't know if we have a strong enough society or motivated enough populace for guerrilla war. We could make ourselves a hard enough target for them to avoid if we invested heavily in expanding the military, but where are we going to get the weapons? America? They could turn them off remotely I'm sure. China would be a good option, but America might invade us right away once they found out we were doing that. It's a big problem.
Even if we could get the Europeans to do anything more than write a strongly-worded letter, they don't have much in the way of military might themselves. Frankly, I don't trust them to help unless something changes, but the ticket is deterrence. We need to make ourselves a hard enough target that the Americans aren't willing to try to take a bite, and it's going to take a combination of alliances (we should ally with Mexico, since America is coming for them too) and armaments.
Regarding shifting social spending to defence, I think it's a bad idea, at least without other major changes elsewhere. Part of our problem is motivation - we've had 40 years of neoliberalism telling us the state owes us nothing besides tax credits and we owe the state nothing besides paying our taxes and obeying the law. We're already halfway to losing public healthcare, so we won't even be able to fight for that. We need a fundamental paradigm shift to save this country, and I'm not sure if we have the will or the imagination.
I agree, the separatists should go on down to the US