I thought it was impossible too for my plan, but then I found a good flow chart on the government website for the bureau of agriculture in my home country. If Brasil is similar it will be long, arduous, and plenty of hurdles but not impossible. You would need the US import permit for plant material. Then you would need to buy the trees, make sure the species are allowed. Take it to one of your offices in Brasil, they will give your material the inspection. Then they may quarantine it. They will either issue you a phytosanitary certificate or destroy it, or give it back to you to give away. Then you will carry your permits, phytosanitary certificate, and the labels from your usda office. You will clearly mark your package, run it through Brasilian airport. This may get tricky if you need to layover. You may need a permit to transport the material. If the flight goes straight to the US then you may not. Then when you arrive in the US, you will need to present your plants and permit and phytosanitary paper to the usda office in the airport. The office needs to be open. Then they will inspect the plants and either let you through, quarantine, or destroy them.
I think that's the meat of it. There's obviously more to it, but if you think that's too much, then you won't care to know what more you may need to work on.
