Justifying doing something wrong by stating that someone else did equally bad or worse is not a valid argument.

By this reasoning, some random EU country could raise co2 emissions, stating that China is even worse. Problem is: the Planet does not care about artificial, man made boundaries.

To your last question: Yes, you should feel responsible. Who else could be? The point is to be conscious about what you do. Not everybody can be the best version of oneself, all the time, me included. However, denial is probably the worst of all reactions to this problem.