Academia is appealing because it often provides better job security, and the range of research opportunities is much wider. Industry is often much better funded, paying researchers more and giving them better resources for their research. In most cases, the decision really boils down to the job offers you get.
One of the main reasons to choose academia over industry is that you have a lot more control over what you research and/or study for your job. Another driving motivation is the desire to contribute to educating younger generations. You might also prefer the academic environment and the chance for tenure.
It is possible to fail a PhD defense, and it does happen every now and then. For the most part, this only happens when a student defends without sufficient support from their advisor. Either the advisor failed in their role, or the student blatantly ignored the advice and defended before they were ready.
The big difference is in the path to obtaining the PhD degree. In the US, a bachelor’s degree is usually required to get into the PhD program. While you can’t normally apply to the PhD program in Europe without a master’s degree. Both PhD degrees in these two regions, however, are recognized in either region.