I have quoted a couple of such studies in my recent question Have Netanyahu's policies fueled a rise in anti-Israeli sentiment? - see below.
Longitudinal, cross-sectional a,d cohort studies
As @Fizz have correctly pointed in the comments, there is some ambiguity about what we call a longitudinal study - in psychology and medicine this would mean following up the same persons', asking their opinion from time to time, to see how it evolves. In this sense the Gallup studies are not longitudinal, but cross-sectional ones - taking a sample of opinions at different monets of time, not necessarily with the same persons.
However, from the sociological viewpoint we are interested not how the opinions of individuals evolve, but in evolution of the public opinion as a whole. In this sense the Gallup studies are longitudinal, while the above mentioned psychological/medical studies are more precisely referred to as cohort studies (following a cohort of the same persons.)
What is "view"?
One may also questions what it means a view on the conflict: what studies analyze is moire the sympathies and the support, but most respondents likely share the same view: achieving peace. Furthermore, most westerners likely agree that two states for two people living in peace and security is a just solution, regardless of which side they sympathize with more. Some fringe groups may support one-state solution or three-state solution, and the support for the former is likely higher in Europe, where EU integration is viewed as a guarantee of European peace (although arguably it was originally an economic rather than political union.) Even smaller minorities might promote eliminating one of the conflicting groups altogether - this view is however rather widespread in the Middle East, and championed by such notorious groups as Hamas; however it is completely antithetical to western values/
Examples
A couple of graphs from Gallup:
From 2010 report Support for Israel in U.S. at 63%, Near Record High
From 2022 report Americans Still Pro-Israel, Though Palestinians Gain Support