@ChinaVoodoo is correct. Whole leaf tobacco is treated like any other agricultural product like tomatoes, corn etc... so I don't see how they could tax it without taxing all agricultural products. Now, tobacco products (whole leaf tobacco that has been processed in any way) are another issue but if that happens you have already identified a convenient way around that tax. It would also spell great news for whole leaf distributors as I imagine their sales would sky rocket! Any minor world that breaks apart...
You can never tell with the U. S. Government, they can tax whatever they want, whenever they want, however they want, the same way as they give subsidies in strange ways as well. As noted before, taxes can be imposed at any fiscal transaction point on any product that can be identify as needing to be regulated as well as imposing a "sin tax" to cover all bases. How other countries do it is besides the point. A few days ago I had a conversation with someone in Europe and there are countries that have taxed tobacco out of existence in some countries. The U. S. tobacco industry may or may not be able to deflect the actions noted in the bill, but it sounds like they were sort of staying on the sidelines for right now. Look what was done to the cigarette industry in the 90's with the lawsuits that fined the heck out of them. The industry survived, despite paying billions and billions, but that cost was loaded back onto the products.
In regard to what tobacco products they are focused on is still pretty vague, and I believe that is intentional so as to allow more room for maneuvering. This bill has been tried before and failed, but it failed because there was pushed back on it. Likewise now, if there is no pushback, then it could succeed. They could be eyeing the end product (pipe tobacco or cigarette tobacco), or could move the focal point as far as needed to capture different fiscal transaction points to address (in their view) the real source(s) of the product.
"Spirit of the law" notwithstanding, they are not concerned about industries, but about their constituent's. If other agricultural product like tomatoes, corn, etc could be shown to cause health issues, then they would be looked at closer thru a looking glass as well.
Anyway, want to keep this from becoming political and I don't want to be banned from the site.
Just my two cents worth
Cheers