It's not necessarily pro-War or pro-American. Obviously, WWII itself was "necessary" (though the U.S. only got involved when they were attacked in Hawaii, even though they were aware of what was happening to Jews in Germany and Poland for years), and America was on the right side, but the film is written on a very simplistic level. The characters, aside from Hanks, are far from three-dimensional, and there's a whole lot of cliche going on in the film.
What's cheesy are the bookends, and the way the old man cries as he asks his wife if he was a good man is just nauseating. It was clearly designed to make every veteran (and every veteran's family) cry in the theatre, and I just think it's cheap. Plus you have the flag waving at the end and it's just so phoney and over the top.
The Thin Red Line, on the other hand, doesn't talk at all about heroes, earning the sacrifice of others, or any of that bullshit. It attempts to get in the heads of the soldiers and find that soul that connects all of them, even while the experience itself shuts them off from others (something that continues when the war is over) and how that soul is tainted as war takes its toll on the individual men and the environment around them. It's a much more universal and sophisticated message than what Spielberg is peddling. It's also a lot more cynical about why the wars are really fought and the fucked up things people do during them. And I might add that the novel TTRL was based on was written by a guy (James Jones) who fought himself at Guadalcanal (and also wrote From Here to Eternity). This is his inscription at the front of the novel:
"This book is cheerfully dedicated to those greatest and most heroic of all human endeavors, WAR and WARFARE; may they never cease to give us the pleasure, excitement and adrenal stimulation that we need, or provide us with the heroes, the presidents and the leaders, the monuments and museums which we erect to them in the name of PEACE."
I didn't find that bitter, ironic sentiment ANYWHERE in Saving Private Ryan, and that's what prevents it from really representing the full scope of war. Perhaps it wasn't trying to, but I feel the films that give a more realistic and comprehensive portrayal deserve more credit. I think what SPR does represent is exactly the target that Jones is aiming his words at.