If I'm right, it's mainly because many States on the USA don't have VAT on importation. So, you're very lucky to avoid to deal with them.
Until now, I was just unhappy with UPS' fees, but they were fine on the rest. But...
I just had the worst delivery experience with DHL these past days, with an order from UK to France, because of the Brexit. DHL tried to charge me with a VAT 30% higher that it should have been. I'm not speaking of their fees, but the regular VAT. Add both and it was 50% of the price of my order... But it's another story.
The VAT thing was just absolutely staggering. They employed all the means to get the undue money.
All this was in a time frame of 3 days.
1 - 13 April : I had to pay before the packet can be processed further. I got the bill and didn't agree and contact them to clarify the amount.
2 - 13 April : As they were "kind", they paid for me, so it can be processed. I never asked them to do it. But they were waiting for the payment to deliver the package. It was fine, it lets me the time to get it sorted.
3 - 14 April : They sent me 4 mails to pay. They sent me 3 SMS to pay.
4- 14 April in the evening : They called me. They invented the "VAT based on the weight on the package". I disagree, because it don't exist, and ask them for the 4th time to justify how they manage to have a +30% VAT. My package was still on hold. And it was fine for me.
5 - 15 April at 6:00 AM: SMS to pay. Hopefully my phone was in silent mode.
6 - 15 April at 9:15 AM: SMS and mail because the packet was out for delivery. Remember point 1, 2, 4? Okay. You see point 8 coming? I guess.
7 - 15 April at 9:45 AM: I phoned them and they "stopped" the delivery, so I can contest the VAT.
8 - 15 April at 10:45 AM: the delivery guy phoned me to deliver the package and get the money...
I had no other choice than to refuse the package, which is now back at the sender. I had 5 peoples from DHL on phone, no one knows how the VAT was calculated. When you just had to take the order bill, the postage cost, add them and get 20%. Period.
I've been told by the sender that they are closing their deal with DHL, as many, many of their customers are facing overcharge from them. So it's a huge problem for them as many of their customers are in Europe, they're losing big money.
Clearly, DHL and the others are killing the trade.