What the hell are Black Widow & Hawkeye going to do?
I think the bigger problems would be Vision, Wanda, Cap, Spiderman, etc....they are still alive and would probably respond to a hyper advanced country literally popping out of nowhere trying to dominate the world.
Anyway you should probably watch avengers 1 and 2 before infinity war drops because clearly you haven't seen it. If you did you would know that hawkeye and black widow would take out damn near half of the Wakandan army. Why? Because its a damn comic book movie and those two characters are written that way. Whether it makes sense or not, that's just how it is. Tell me I'm wrong...