Seems like when the snap happened, it was daytime in the USA. There are two pieces of evidence you can see prior to Endgame.
The first one is the post-credit scene of Avengers: Infinity War, where Nick Fury and Maria Hill were disintegrated. It was daytime there too.
The second one is the mid-credit scene of Ant-man and the Wasp, where Hank Pym and his family were disintegrated after Lang got stuck in the Quantum Realm. It was daytime too.
There is no timezone specified in MCU, but it could be UTC+3 as it said to be located near East Africa.
From Express article,
While its location has varied in the comics, the Marvel Cinematic Universe appears to place it where Marvel Atlas No 2 does – namely in East Africa.
Considering timezones in the USA, the time difference between Wakanda and the USA is between 7 hours to 10 hours which is usually a length of a normal day. Wakanda is ahead of USA, so when it is morning in USA, it will be dusk in Wakanda.
In conclusion, it is possible when it's daytime in Wakanda, it can be daytime in the USA as well.