Based on Gallup surveys. 33% said aliens in 2019. 41% said aliens in 2022.

Criteria: Resolves based on first post-January 1st, 2025  Gallup survey asking  "We have a question about unidentified flying objects, also known as UFOs. Which comes closer to your view -- [some UFOs have been alien spacecraft visiting Earth from other planets or galaxies, (or) all UFO sightings can be explained by human activity on Earth or natural phenomenon]?" 

https://news.gallup.com/poll/350096/americans-believe-ufos.aspx