Companies will pay bribes to officials to allow them to sell their products in the country that they enter. People think about bribes as being a way for a company to avoid legislation, exposure or fines. Sometimes companies pay bribes in other countries in an attempt to change small issues that could hurt the company in question. Bribes are sometimes used as a way to sway a direction when deciding on what company should take a contract.
If you wish to understand corruption, you need to understand some of the differences in culture between countries. In many individualist countries, the offering of inducements to individuals is seen as corruption, whereas in many collectivist countries, it is seen as part of normal business practice. Clearly, when such inducements become large (in proportion to the value of the associated goods or services), the economy becomes seriously affected, and poverty increases.
Western multinational companies are continuously exhorted to respect national cultures, so the issues associated with inducements cause many problems for them. I do not intend to imply that inducement-offering companies aren't 'the bad guys' - they are proliferating what I regard as bad practice; it's just that the background to what Westerners label 'corruption' requires much more understanding before it can be tackled. Changing 'the guy at the top' will have no more than a temporary effect if overall culture is unchanged. As for changing regulations, it is only in typical individualist countries that regulations, in reality, apply ~equally to everyone.
I would thoroughly recommend that anyone with an interest in corruption (or any issue that arises across multiple nations) spends half an hour at one Hofstede's websites, and perhaps looks at the cultural frameworks of other key people in the field of culture (e.g. those of the GLOBE Project, Trompenaars or Schwartz). If you want to know more, then Hofstede et al's book 'Cultures and Organizations', 3rd edition, will give you many "... Ah, that explains it ..." moments.
In my previous university department, we often had to inform pleasant, honest foreign students that the offer of presents to lecturing staff immediately prior to examinations would be considered as corruption on the part of the student.
I have visited the USA many times; in general, the payment of tips there is not associated with corruption - tips are paid to low-paid workers (e.g. restaurant waiters) AFTER the receipt of service from them, and are dependent on actual quality of service. I have no doubt that there is corruption in the USA, but the payment of tips is not related to that, any more than the payment of daily tips to hotel room cleaners in the Philippines is related to Filipino corruption.
Obviously, the above-mentioned 'individualist/collectivist' split is a gross simplification, as we should also consider power distance, uncertainty avoidance, per-capita wealth, etc., but space limitations prevent a long discussion.
It takes a brave researcher to write about the international aspects of corruption because such a researcher runs headlong into the barbed wire of political correctness! Good luck.
PS. There are many blogs that provide insights to corruption, but you have to treat the information with caution.