The #1 most relevant goal for politicians is to get re-elected. (Personal enrichment is largely orthogonal.) Raising large campaign contributions is of obvious benefit to that effort, and is not directly a bribe per se. But it does have some of the same problems that bribery has.

It’s undoubtedly true that some US politicians have gotten bribes, defrauded partners or constituents, embezzled money from their campaigns or the government, used inside information to trade stocks, etc. But even if all of those were impossible, the nature of the US campaign finance system would create plenty of perverse incentives.