The fentanyl and fentanyl analogues that have spiked opioid overdoses in the past few years are coming via mail from China and Canada. Literally hundreds of people have died in the span of two nights from batches of heroin laced with cheap internet fentanyl derivatives. The people selling cheap internet fentanyl laced heroin aren't cartels or minority run gangs, they tend to be in the 16-28 demographic of white-bread drug dealers with access to a computer. The margins make sense (a dose of fentanyl can be as cheap as 1/100 of a penny when dealers pick it up in bulk vs the more expensive gang-sourced heroin) and attract people without many opportunities nor the education/ qualifications to make sure they can accurately sell people micrograms of a powder and not kill them. People like our friends might be or might have been.
Different gangs and supply chains bring heroin into different areas of the country. Some areas still have Afghan heroin coming in, perhaps from the same fields we protected from destruction while we were over there.
I lean left and come from a background very similar to yours. There is a difference between acknowledging the importance of ignored issues in these areas and saying "this is why Trump won".