Clarification on USA flying?

[MichaelJP59]

I know that the rules are a lot stricter for flying in the US now and you need an M1 visa for flight training.

As a student PPL though, can I take an "experience flight" with an instructor in the USA having entered on just the usual visa waiver?

Presumably there would be no argument about me taking a flight as a passenger in the same light aircraft so where is the line drawn? Is it if I am taught anything?

Thanks for any help.