You are equating two different things. One, giving a politician money they can spend on personal luxuries for a political favor. Two, giving a strictly-regulated campaign money it can spend on advertising, political functions, et cetera, or less-regulated PACs.
Personal versus political benefits is one major diffference. Prevalence, and the necessity of engaging with corrupt organs to survive and thrive, is another.
Claiming corruption in America even rivals most of the world is unsubstantiated. The inverse is well substantiated.