The United States is strict and skirting the law doesn't guarantee protection. They also keep records of all mail moved through U.S.P.S. (U.S.P.S. handles E.M.S.) and take photos of the outside of packages. Domestic mail has greater protections than international mail. The vendors online store or emails being monitored could result in domestic seizure. They can open international mail without warrants if statistical data or anything else indicates the sender or recipient is suspicious.
Motion Research sold unscheduled chemicals domestically such as 25i-NBOMe "Not for human consumption" before they were scheduled. Saying 25i-NBOMe is an analogue of 2C-I is stretching the concept. The IT guy got 17 years and the owner is being sentenced today.
The analogue laws get interpreted very flexibly and the possibility of having a seizure, getting a knock on your door, or having the mail man "accidentally" drop your package and tear it open while getting chased by the neighbors dog is real.
Mushroom spores are legal. Acacia is questionable as some species grow wild in the United States. You could order these domestically using public wifi, disposable email, and prepaid card bought with cash while your house was empty of paraphernalia. If they ask you to sign for the package just tell the postal guy no. These steps minimize risk.
