For issue one, that is less of an issue than you might think.
Without the US to play world police, other nations would have to actually pay for and build thier own defenses, deal with thier own economic shit, and feed themselves.
Also, I think France would love be able to supplant the US as the dominant Western power, and with the EU they have the power to do it.
As for issue two, yes, they get a vote; however unless they want to mount an invasion of CONUS it doesn't mean much, and even a Balkanized US/successor states would likely be able to fend off any serious attempt by a foreign power to invade N. America.
You can all keep acting like the US is Atlas holding the world up, I'm not that naive or blindly nationalist.