While anti-biotics are (or their misuse rather) is clearly a big problem I don't see them being to blame for this trend of disease spreading with "westernization". Personally I'd attribute that to crap diet (BigMac & Coke) and sedentary lifestyle.
That's the popular theory, but there is some evidence that the issue is more complicated than that. E.g. diets are incredibly ineffective at losing weight. People artificially forced to gain weight by eating a lot quickly return to their previous weight after they stop. And identical twins maintain very similar weights even when they are raised in separate environments. And lab animals have actually gotten fatter over time for unknown reasons.
Medical professionals are just starting to take this stuff seriously and we have only recently started studying the human microbiome [1]. Whatever existing information and biases you're using for your personal opinion are probably just as flawed.
