While it's true that there are U.S. states where it's illegal, there are many places (maybe most?) where it's not. Presumably due to the fact that it's near impossible to prove in court unless they were giving out receipts that said "bribe for business deal" on them or something. Otherwise there's almost no scenario where you can't say "we're friends and they gave me a gift, I chose their company for the contract because I thought they were the best choice."
> While it's true that there are U.S. states where it's illegal
Its over 2/3rds of states and includes most major ones have laws against commercial kickbacks. Even in states that aren't you could be charged with fraud under state law.
> Otherwise there's almost no scenario where you can't say "we're friends and they gave me a gift, I chose their company for the contract because I thought they were the best choice."
This argument is silly. It applies equally to federal laws that are frequently used to prosecute kickbacks for government employees, contractors and subcontractors. There are plenty of ways to charge someone with kickbacks besides idiotically labeled receipts.
Just because you think you can get away with something because it is hard to prove, doesn't make that activity legal, let alone moral/ethical.
Many states have laws that explicitly target commercial bribery. Even where those laws don't exist, various fraud laws can also apply.
I don't know if there is specific precedent here, but your broad assertions are quite incorrect as even a cursory google search will reveal.