idk, some countries it would destroy but if it starts out in a smaller country the major powers could align in a time of need (yea right) and put down the invasion by sheer fire power.
for example there was like 100k troops in iraq at one point. if we have 100k professionals with m-16s and what not plus other countries and militia i think we could survive.
only if the world worked together LOL
modern technology would also give us a huge advantage.
plus time to include mass evacuations might be had if the outbreak starts in a small distant country.
just my 2cents