Always On Availability Groups Network Configuration in AWS
In AWS EC2, you don't get the ability to add additional network ADAPTERS to your VM.

You can add additional network INTERFACES, which are just different IPs/subnets/routes/etc, but they're using the same underlying network adapters (cards).

You can choose to use instance types with faster networking ports, though. The EC2 instance configuration page lists which ones have 10 Gigabit ports, although I like ec2instances.info for easier sorting and filtering. When you're doing Always On Availability Groups, it's especially important to use this faster networking because high-network operations (like backups to another machine) can result in SQL Server timeouts (disclaimer: that's my blog post) if you've only got GbE networking. (That causes AG failovers.)