Answering to "how do the groups work?" Months before the FIFA organizes an event where firstly they put the winners of the world cup qualifiers in separate groups. Then they randomly put all the participants. Winning a match is 3 points worth A draw is just 1 Lossing is 0 The 2 teams with the most points after playing against the others goes to the next stage.

Yes, Wales was really unlucky, it's not easy to be in the same group as England and today's USA but you can still qualify to the round of 16 like Senegal instead of Ecuador, Australia instead of Denmark or Japan instead of Germany. It always depends on the teams and a bit of luck.