The Asus Zenfone 6 will soon be available in the US. B&H has it available for pre-order – here’s the link – but note that the shipping date is yet to be set.
The 64GB model costs $ 500 and while the phone has a microSD slot, you may want to go up to the version with 128GB storage anyway – that’s $ 550. Both versions come with 6GB of RAM. By the way, the card slot can house two SIMs in addition to the microSD card (it’s not either-or like with hybrid slots).