Their 15% is a federal sales tax, not a state sales tax. That money goes directly into Mexico's federal coffers. That's where the tax money, that Trump is proposing, will go. And, it will pay for the Wall.
On everything. So if we do that, then your car will also get a 15% sales tax even if it's made in the States. That's what a VAT does in Mexico. It's just an additional sales tax on everything.
Now, if Trump decides to implement some kind of Tariff and it helps, great!
If it hurts, people are gonna be kinda pissed.