Which app is used to communicate with friends in US

Discord, Instagram, Snapchat, and Apple iMessages are all commonly used in the US. GroupMe and WhatsApp exist as well but aren’t as heavily used.

My teenage students use Discord and their phones' texting apps.

Americans connect with each other via text (SMS or iMessage). Facebook messenger is also used, or DMs on Instagram. Snapchat is much less popular than it was years ago, mainly used by teenagers. Telegram and Signal are very infrequently used. WhatsApp is not very common, more likely to be used by people that have family in other countries. The majority of people only use texts.

As somebody else already mentioned, it depends on the age of the person. I'm 18 and I connect with my friends via SMS, Instagram and Snapchat.

don’t take the advice of people in the replies and ask people for discord, most people would use snapchat if they’re younger or instagram dms or imessage

What friends?

i personally would prefer discord or telegram

I still use Snapchat but I have had to make a discord as well as some people don’t use Snapchat or Instagram anymore. I still don’t really understand it though lol

iMessage and SMS.

we use different apps depending on the age of the person you're speaking to or the kind of chatting you're doing. as I understand it, Whatsapp is the default way to text in many countries. in the US, Whatsapp is mostly used to speak to people abroad. when texting each other domestically, we use the texting app on our phones to SMS or RCS (iMessage, Google Messages, etc)

My phone's default text messaging (sms) app. That's overwhelmingly the way people communicate here. Especially anyone over 30.