Funnily enough my circumstances are similar. I just started a new game Normal level and was also excommunicated for Warring with France. All of France is under my control so being allied with Spain and Aragon, among others, i moved against HRE and took two provinces. The following year Spain broke the alliance and declared a crusade against me.

In good ol domino style all my allies cancelled their alliances with me except for Hungary. Italy broke their alliance the same turn as they accepted a royal marriage with me lol.

Anyway i have to move all my forces to the Spanish border while leaving just enouth to defend against HRE attacks. Fought my first battle in Navarre. 400 Spanish vs my force of 1300. My General broke fighting with his 60 Militia against the spanish king on his own! Soon my entire army followed suit and it was embarrassing! I then quit the game without saving lol