On multiple occasions in my life I've needed to order extra pages for my passport because it was full of stamps. I've been to every continent except for Antarctica and 50 plus countries and have literally never had a negative interaction because of my nationality.
Maybe you need to travel more? You hear "Americans are hated" by.... Americans mostly. And, I would guess, Americans of a certain political bent that say it more as a badge of their identity rather than it being an honest belief in the truth(literally "America's #1!!!", but for liberals). It's a grade school level understanding of the world(as is "America #1") and I find it a fair indicator of stereotype-oriented thought patterns when I hear it.