Marine Le Pen Vs. Emmanuel Macron

[Elldallan]

If France elects Le Pen, they'll be pulling out of the EU, which means the EU will either end, or be pretty insignificant globally.
(For anyone curious why this is a big deal)

I don't think the French President has the power to do that without a vote in parliament, and as she controls something like 0.35% of parliament...

I don't think you're quite understanding the idea of secession. If a state decides that things are so bad and they decide to seceed, they no longer acknowledge the laws of the United States, making a US law against secession a moot point.

The point of the law is to make it very clear that secession will be met with an invasion and a reclaiming of the state (s) and it's people. That however is a separate issue entirely from States being "allowed" to seceed. Of course they can, but the consequences most likely wouldn't be worth it.

Ironically, false.

Well there also has to be political will to fight a civil war which is anything but certain. And with other nations throwing their support for the defecting side just to interfere things could turn very very nasty very fast. And of course the loyalty of the military cannot 100% be relied upon in such a situation, it would be a disaster to morale to have to fight your former comrades in arms.