To attempt something is to try to do something or make an effort to do something. You could say "I'm going to try to climb this mountain" or "I'm going to attempt to climb this mountain" In your example it's saying "The European's made efforts (to do something) but those efforts were met with rebellion"

I feel like there is something wrong there because the phrase certainly doesn't seem correct or hold a different meaning like that. Instead of "was", it should be "were" as you said since "attempts" is plural, so I don't know what to tell you. Maybe you misheard it, or the movie itself was wrong, but anyways, I would advise you to double check it if possible.

It simply means they attempted something more than once ..the Europeons attempts to defeat the colonial states was met with fierce resistantance .