What the hell is wrong with amazon regarding ps4?
Or is the switch really beating ps4 so hard in the usa?

There's definitely something going on but it's something more than just Amazon not stocking properly.
Here's an article from last month.

What started with God of War going out of stock on Amazon UK seems to have escalated over the past few days, as now it's impossible to purchase PlayStation Network vouchers from the popular retailer in the USA as well. The cards - which are delivered instantly via email - are available in various monetary increments and have been glued to the top of the site's best sellers list since the PS4 launched.
In fact, Amazon.com seems to be in the exact same situation as the British branch, with God of War constantly going out of stock, and other exclusives like Detroit: Become Human and Spider-Man unavailable at the time of typing. MLB The Show 18 has never been available at the retailer either. Exactly what's going on is still up in the air, but we've once again contacted the platform holder for comment, and we'll let you know if we hear back.
Update (22:00 BST): It looks like PSN vouchers are available once again on Amazon.com. Exclusive games like God of War and Spider-Man are still currently unavailable. The situation on Amazon UK remains the same.
PlayStation's Relationship with Amazon Worsens As PSN Codes Are Dropped - Push Square

Hmmm.  Wouldn't be the first time Amazon had a petty squabble with one of the big 3.  For a while they would not stock certain Nintendo hardware, iirc.

Nah, Amazon is exhibiting weird stock issues.  This will probably be Amazon's least accurate month in years with regards to predictive value as a result.  Cause I assure you even if Switch edges out a victory, no way is Xbone *that* competitive with PS4 right off the heels of GoW.

Its unfortunate that Amazon has changed from being the go to place to now we just don't know. And if you look, its not just with Sony consoles, Xbox One X seems to have stocking issues as well.

Walmart, BestBuy and Gamestop all have regular PS4's (Walmart both 500GB and 1TB), PS4 Pros, and Sony games all shipped from their respective companies and in Walmart's case, two day shipping without the need for a membership.

The backgroud color as telling where it's doing the best and worst, atm is manually. Will try to find a way to make it automatically. 

That's strange. That Italian's taste.

Switch keeps on climbing. I think Nintendo are going to have a pretty big E3 this year. Only with smash they can bring up the hype level for the Switch and there is no way we won't have any other big titles.

Also think, if the rumours are true, that the Retro game will surprise people. They are so talented and the game seems really meaty so I'm not scared for this title. But that pokemon game will be disappointing i knew it since it got announced and it seems even worse than i could imagine from the rumours. Switch will most likely have a boost still but honestly i think gamefreak should do a heavy dust sweeping on their crew members cause they keep on making such terrible decisions.

Top 10 full of Switchness!! Could May be THE month?

Not according to the NPD predictor thread. We should be looking at that thread for a better picture since we already know that Amazon is heavily skewed towards Nintendo. 

Once symbois fine adjusts that thread, it could be something really reliable.