You can do that in US too. You can take itemized deduction (similar to A you mention) or you can take standard deduction which is flat amount (similar to B). But the US government lets you apply many more deductions after taking either of these and that is where the complexity comes. You can choose to do just itemized or standard deductions in US and not bother about other ways of saving money and then your taxes will be simple like Taiwan. That's your decision.